I dropped the version constraint in web-console with the idea it will be
easier to upgrade the console between Rails releases. However, issues
like #25899 started popping up.

I'm reintroducing the constraint, but this time, I don't set an upper
limit to the major version. This will keep the web-console in a version
that always works for the current Rails version and can be easily
upgraded to the last one with `bundle update`.

We may need to backport this for Rails 5.0.1.

Fixes #25899.

- By default the session store will be set to cookie store with
  application name as session key.
- Older apps are not affected as they will have the session store
  initializer generated by Rails in older versions, and Rails will not
  overwrite the session store if it is already set or disabled.
- But new apps will not have the initializer, instead the session store
  will be set to cookie store by default.
- Based on comment by DHH here - https://github.com/rails/rails/issues/25181#issuecomment-222312764.

Since bundler 1.12.0, the gemspec is validated so the `bundle install`
command will fail just after the gem is created causing confusion to the
users. This change was a bug fix to correctly validate gemspecs.

- Adjusted tests instead.

Fix minor regression about old apps not getting per_form_csrf and request_forgery_protection configs

- Earlier per_form_csrf_tokens and request_forgery_protection config
  files were generated for old apps upgraded to Rails 5.
- But when we collapsed all initializers into one file, the entire file
  does not get created for old apps.
- This commit fixes it and also changes values for all new defaults for
  old apps so that they will not break.
- Also added a test for `rails app:update`.

- Adjusted tests also for this new behavior.
- Based on the discussion in
  https://github.com/rails/rails/pull/25184#issuecomment-222454583.

- These initializers are new defaults for Rails 5 and newly generated
  apps do not need to change them.
- Fixes #25181

In Ruby 2.4 the `to_time` method for both `DateTime` and `Time` will
preserve the timezone of the receiver when converting to an instance
of `Time`. Since Rails 5.0 will support Ruby 2.2, 2.3 and later we
need to introduce a compatibility layer so that apps that upgrade do
not break. New apps will have a config initializer file that defaults
to match the new Ruby 2.4 behavior going forward.

For information about the changes to Ruby see:
https://bugs.ruby-lang.org/issues/12189
https://bugs.ruby-lang.org/issues/12271

Fixes #24617.

* Updated syntax

* Updated tests to match syntax

[related #24243]

- While working on https://github.com/rails/rails/pull/22790 I found out
  that we pass `with_dispatchers: true` but it's not used at all by Rails.
- We were passing `with_dispatchers: true` in few tests too but again
  it's not used by Rails.

Between major versions 2 and 3, we hit a bug. It's fixed in version 3,
however, the explicit 2.x requirement of `~> '2.0'` will prevent people
from getting the fix with `bundle update` and they would have to
explicitly set the constraint to `~> '3.0'`.

For more information see: rails/web-console#178.

I propose we drop the explicit version constraints in the Gemfile. Web
Console has been relatively stable for the past couple of years, and I
don't anticipate any major alterations, like we saw between major
versions 1 and 2.

In order to eliminate the dependecy of CoffeeScript.

Rack cors initializer is only necessary to API-only applications, for when the update is unnecessary.

Puma 3.0 and up introduced compatibility to read from `config/puma.rb` when booting from the command `$ rails server`https://github.com/puma/puma/pull/856.

- We will remove the initializer for old apps which are migrated to
  Rails 5 so that they are not affected by this breaking change.

This also marks Action Cable routes as internal to Rails.

- app generate option --skip-sprockets leaves jquery-rails gem, which relies on sprockets environment
- Remove jquery-rails if --skip-sprockets is true

Fixes #23431

Redis now included in Gemfile but commented out. This change was made in
91864439 and is causing the test
failure.

See https://travis-ci.org/rails/rails/jobs/106994913#L1025

Test of Rails API should be in `api_app_generator_test.rb`.

This new adapter does get a little more intimate with the redis-rb gem's
implementation than I would like, but it's the least bad of the
approaches I've come up with.

When the `puma` command is run without any configuration options it will detect presence of a `config/puma.rb` file and use that. Currently there is discrepancy between `puma` command and `rails server` but Evan said it would be reasonable to add in reading in config from the default location. I am working on that right now as a feature in puma/puma.

Why do we need this? By default Puma uses 16 threads, and by default ActiveRecord only has 5 threads. Due to the architecture of AR it is guaranteed that if you're running with fewer DB connections than your server has threads you will hit `ActiveRecord::ConnectionTimeoutError ` eventually if your app gets modest amounts of traffic. Since we are providing a default webserver, we should provide reasonable configuration for that webserver.

This PR does a few things, first it sets the default Puma thread count to 5 to mach ActiveRecord's default. It sets the default environment to `"development"` and the default port to 300 so that booting the server with `$ puma` will give you the same default port as `rails server`. It is worth mentioning that by reading in from `PORT` environment variable this config can work with containerized deployments, such as on Heroku. 

We are not using worker processes by default, that way JRuby and windows devs can use this configuration without modification. I went ahead and included a default `on_worker_boot`. It won't be used unless a worker count is specified, that means this config will not use it. Even though it's not being used now It will make someone who wants to try modifying their config to run extra workers easier.

cc/ @pixeltrix

It was removed by mistake at 877a411d

`rack-cors` gem is defined in Gemfile by default only if the api,
not defined by default in rails app.

The Action Cable generators creates four files which need to be removed
if `skip_action_cable` is set.

1. `app/assets/javascripts/cable.coffee`
2. `app/channels/application_cable/channel.rb`
3. `app/channels/application_cable/connection.rb`
4. `config/redis/cable.yml`

Fixes #22669.