ref https://bugs.ruby-lang.org/issues/8846

- Changed `IN` to `ON` in all note sentences in guides.

This stems from [a comment](rails#17227 (comment)) by @dhh.
In summary:

* New Rails 5.0 apps will not accept `return false` as a way to halt callback chains, and will not display a deprecation warning.
* Existing apps ported to Rails 5.0 will still accept `return false` as a way to halt callback chains, albeit with a deprecation warning.

For this purpose, this commit introduces a Rails configuration option:

```ruby
config.active_support.halt_callback_chains_on_return_false
```

For new Rails 5.0 apps, this option will be set to `false` by a new initializer
`config/initializers/callback_terminator.rb`:

```ruby
Rails.application.config.active_support.halt_callback_chains_on_return_false = false
```

For existing apps ported to Rails 5.0, the initializers above will not exist.
Even running `rake rails:update` will not create this initializer.

Since the default value of `halt_callback_chains_on_return_false` is set to
`true`, these apps will still accept `return true` as a way to halt callback
chains, displaying a deprecation warning.

Developers will be able to switch to the new behavior (and stop the warning)
by manually adding the line above to their `config/application.rb`.

A gist with the suggested release notes to add to Rails 5.0 after this
commit is available at https://gist.github.com/claudiob/614c59409fb7d11f2931

Arguments of Bundler.require of generator has been changed from rails4.0.4.

https://github.com/rails/rails/blob/v4.0.4/railties/lib/rails/generators/rails/app/templates/config/application.rb#L16

References #18148.

[ci skip]

Closes #17965, #17968

[Godfrey Chan, Miklós Fazekas]

This reverts commit b0e7278d, reversing
changes made to 785d04e3.

This is not true. It is a bug and we will fix in the latest 4.0.x
release.

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

Update to consistently use American English [ci skip]

- Everywhere else we using HTML Sanitizer except this place.

[ci skip] Fixes typos in section 2.7 "Rails Html Sanitizer", adds content to section 2.8 "Rails DOM Testing"

[ci skip]

- [ci skip]
- behvaior -> behavior

Also add to upgrading guide a notice about the deprecated sanitizers

This seems to be the style settled on in most of the templates.

minor fix for #16846

- Part of 16576
- [ci skip]

Goals:

1. Default to :random for newly generated applications
2. Default to :sorted for existing applications with a warning
3. Only show the warning once
4. Only show the warning if the app actually uses AS::TestCase

Fixes #16769

Related: https://github.com/rails/rails/pull/16607