Getting the location of the server

[ci skip]

Use web_console 2.0 for 4.2.0.rc1 release

Adding simple docs for ActionDispatch::Flash::FlashHash#to_session_value

This one replaces the notable web-console mentions in guide and the
default Gemfile.

Originally caused by #17771

Closes #17759

If you run a generator such as:

```
rails generate model accounts supplier:references
```

The resulting migration will now add the corresponding foreign key
constraint unless the reference was specified to be polymorphic.

Remove is_a? check when ignoring tables

Local vars should exist in partials for falsy `:object:` values too

Do not rescue Exception in ActionDispatch::ParamsParser

Small fix for the router visualizer

Not sure how we missed this case when we moved everything else to the
`_quote` method.

c67005f2 made the local var in partials
available only if what passed to `:object` was truthy.

For example this would not make the local variable `foo` available inside the
partial:

    render partial: 'foo', object: false

Fixes #17373.

Remove Web Console /console references in the guides

bring back `db:test:prepare`.

The records weren't being replaced since equality in Active Record is
defined in terms of `id` only. It is reasonable to expect that the
references would be replaced in memory, even if no queries are actually
executed. This change did not appear to affect any other parts of the
code base. I chose not to execute callbacks since we're not actually
modifying the association in a way that will be persisted.

Fixes #17730

This reverts deprecations added in #13528.
The task is brought back for two reasons:
  1. Give plugins a way to hook into the test database initialization process
  2. Give the user a way to force a test database synchronization

While `test:prepare` is still a dependency of every test task, `db:test:prepare`
no longer hooks into it. This means that `test:prepare` runs before the schema
is synchronized. Plugins, which insert data can now hook into `db:test:prepare`.

The automatic schema maintenance can't detect when a migration is rolled-back,
modified and reapplied. In this case the user has to fall back to `db:test:prepare`
to force the synchronization to happen.

[Rafael Mendonça França & Yves Senn]

This require caused the `active_record.set_configs` initializer to
run immediately, before `config/initializers`. This means that setting any
configuration on `Rails.application.config.active_record` inside of
an initializer had no effects when rails was loaded through `rake`.

Introduced by #6518

/cc @rafaelfranca

Fixing wrong link in 'Ruby on Rails 3.0 Release Notes' [ci skip]

Combine aliased_table_for and aliased_name_for

Don't center the routes table on routing errors

The tests to verify our testing setup used `RAILS_ENV=development`
to execute the tests. Let's keep it as close to a real-world setup
as possible.