Added controller-level etag additions that will be part of the action etag computation *Jeremy Kemper/DHH*

Add automatic template digests to all CacheHelper#cache calls (originally spiked in the cache_digests plugin) *DHH*

Changes in old branches needed to be manually synched in CHANGELOGs of newer ones.
This has proven to be brittle, sometimes one just forgets this manual step.
With this commit we switch to CHANGELOGs per branch. When a new major version is
cut from master, the CHANGELOGs in master start being blank.

A link to the CHANGELOG of the previous branch allows anyone interested to
follow the history.

Many named routes have keys that are required to successfully resolve. If a key is left off like this:

    <%= link_to 'user', user_path %>

This will produce an error like this:

    No route matches {:action=>"show", :controller=>"users"}

Since we know that the :id is missing, we can add extra debugging information to the error message.

    No route matches {:action=>"show", :controller=>"users"} missing required keys: [:id]


This will help new and seasoned developers look closer at their parameters. I've also subclassed the routing error to be clear that this error is a result of attempting to generate a url and not because the user is trying to visit a bad url. 

While this may sound trivial this error message is misleading and confuses most developers. The important part isn't what's in the options its's what's missing. Adding this information to the error message will make debugging much more obvious. 

This is the sister pull request of https://github.com/rails/journey/pull/44 which will be required to get they missing keys into the correct error message. 

Example Development Error in Rails: http://cl.ly/image/3S0T0n1T3421

we should take disabled option not only from `html_options` hash but from
`options` hash too like `build_select` method does it. So

datetime_select("post", "updated_at", { :discard_minute => true }, { :disabled => true })
datetime_select("post", "updated_at", :discard_minute => true , :disabled => true)

both these variants work now

closes #7431

This functionality will be available from gem
`active_record-session_store` instead.

With a value of "nosniff", this prevents Internet Explorer from MIME-sniffing a response away from the declared content-type.

Updated documentation to demonstrate start_hour and end_hour options

Allow data attributes to be set as a first-level option for form_for, so you can write `form_for @record, data: { behavior: 'autosave' }` instead of `form_for @record, html: { data: { behavior: 'autosave' } }` *DHH*

We recommend the use of Unobtrusive JavaScript instead. For example:

  link_to "Greeting", "#", :class => "nav_link"

  $(function() {
    $('.nav_link').click(function() {
      // Some complex code

      return false;
    });
  });

or

  link_to "Greeting", '#', onclick: "alert('Hello world!'); return false", class: "nav_link"

for simple cases.

This reverts commit 3acdd652.

Revert "Merge pull request #7033 from kron4eg/master". Not a a fan at all of what this makes ERB files look like.

This reverts commit 46b8bcee, reversing
changes made to 2f58795e.

Restoring the '%' trim mode for ERb templates, allowing for a leading percent sign on a line to indicate non-inserted Ruby code.

Rails were including 'application.js' to the pack when using
`javascript_include_tag :all` even there's no application.js in the
public directory.

Passing options as the last value in an array doesn't work with form_for.
This reverts commit 6be564c7.

Rather than keep the url options in record_or_hash_or_array, extract it
and reverse merge with options as it may contain important private keys
like `:routing_type`.

Closes #7259

This applies to the following helpers:
`button_to`
`button_tag`
`image_submit_tag`
`link_to`
`submit_tag`

Also fix some wrong formatting.

Related discussion:
https://github.com/rails/rails/commit/ab72040b74f742b6676b2d2a5dd029bfdca25a7a#commitcomment-1525256

Similarly to 65250022, this allows to use routes helpers for mounted
helpers, but this time in ActionView::TestCase