Update guides for new rendering options

* Introduces `:plain`, `:html`, `:body` render option.
* Update guide to use `render :plain` instead of `render :text`.
Add missing CHANGELOG entry to Action View
Add `#no_content_type` attribute to `AD::Response`

Setting this attribute to `true` will remove the content type header
from the request. This is use in `render :body` feature.
Update upgrading guide regarding `render :text`
Merge pull request #14062 from sikachu/ps-render-format

Introduce `:plain`, `:html`, and `:body` render options.
Sync 4.1 release notes with changes since 7f648bc7 [ci skip]
Merge pull request #14097 from chancancode/sync_4_1_release_notes

Sync 4.1 release notes with changes since 7f648bc7
Escape format, negative_format and units options of number helpers

Previously the values of these options were trusted leading to
potential XSS vulnerabilities.

Fixes: CVE-2014-0081
Correctly escape PostgreSQL arrays.

Thanks Godfrey Chan for reporting this!

Fixes: CVE-2014-0080
Preparing for 4.1.0.beta2 release
Merge branch '4-1-0-beta2'

Conflicts:
	actionview/CHANGELOG.md
	activerecord/CHANGELOG.md
Use the reference for the mime type to get the format

Before we were calling to_sym in the mime type, even when it is unknown
what can cause denial of service since symbols are not removed by the
garbage collector.

Fixes: CVE-2014-0082
Typo fix for unscope
Merge pull request #14098 from Amit-Thawait/master

Typo fix for unscope [ci skip]
cache queries in the Model.find(id) path
Merge branch 'master' into adequaterecord

* master: (32 commits)
  Typo fix for unscope
  Use the reference for the mime type to get the format
  Preparing for 4.1.0.beta2 release
  Correctly escape PostgreSQL arrays.
  Escape format, negative_format and units options of number helpers
  Sync 4.1 release notes with changes since 7f648bc7 [ci skip]
  Update upgrading guide regarding `render :text`
  Add `#no_content_type` attribute to `AD::Response`
  Add missing CHANGELOG entry to Action View
  Update guides for new rendering options
  Cleanup `ActionController::Rendering`
  Fix a fragile test on `action_view/render`
  Introduce `render :html` for render HTML string
  Introduce `render :plain` for render plain text
  Update hash format for render_text_test
  Introduce `render :body` for render raw content
  Don't use `# =>` when it is not the expression values
  Fix the column name [ci skip]
  Document the default scopes change on the release notes, CHANGELOG and upgrating guides
  Move changelog entry to the top, fix examples indent [ci skip]
  ...
Update Docs in favor to use render plain instead of text option
ref #14062
Merge pull request #14099 from robertomiranda/render-text-2-plain

Update Docs in favor to use render plain instead of text option
Fix render plain docs example in AM::Base

The errors were introduced in e220a34e39
[ci skip] Close the meta tag with '/>' instead of '>'

This change fixes the 42 instances of `end tag for "meta" omitted, but
OMITTAG NO was specified` error message that comes up when the full
railsguides are validated.

Full error list at
https://gist.github.com/prakashmurthy/9086679.