Maintain proleptic gregorian in Time#advance

Time#advance uses Time#to_date and Date#advance to calculate a new date.
The Date object returned by Time#to_date is constructed with the assumption
that the Time object represents a proleptic gregorian date, but it is
configured to observe the default julian calendar reform date (2299161j)
for purposes of calculating month, date and year:

  Time.new(1582, 10, 4).to_date.to_s           # => "1582-09-24"
  Time.new(1582, 10, 4).to_date.gregorian.to_s # => "1582-10-04"

This patch ensures that when the intermediate Date object is advanced
to yield a new Date object, that the Time object for return is contructed
with a proleptic gregorian month, date and year.
Switched to use `display:none` in extra_tags_for_form method.

The use of `display:inline` with the content_tag call in the
extra_tags_for_form method potentially causes display issues with some
browsers, namely Internet Explorer. IE's behaviour of not collapsing
the line height on divs with ostensibly no content means that the
automatically added div containing the hidden authenticity_token, utf8
and _method form input tags may interfere with other visible form
elements in certain circumstances. The use of `display:none` rather
than `display:inline` fixes this problem.

Fixes #6403
Remove method redefined warnings for test suite

has_many definitions with "name" as singular and as plural e.g.
  has_many :welcome_posts_with_comment
  has_many :welcome_posts_with_comments

Ruby mentions it with:

lib/active_record/associations/builder/collection_association.rb:65:
  warning: method redefined; discarding old welcome_posts_with_comment_ids
lib/active_record/associations/builder/collection_association.rb:65:
  warning: previous definition of welcome_posts_with_comment_ids was here
lib/active_record/associations/builder/collection_association.rb:75:
  warning: method redefined; discarding old welcome_posts_with_comment_ids=
lib/active_record/associations/builder/collection_association.rb:75:
  warning: previous definition of welcome_posts_with_comment_ids= was here
Merge pull request #13598 from zirni/remove_ar_warnings

Remove method redefined warnings for test suite

Closes #13526
Merge pull request #10634 from teleological/time_advance_gregorian

Maintain proleptic gregorian in Time#advance
Add CHANGELOG entry for #10634 [ci skip]
Allow an absolute controller path inside a module scope

Fixes #12777
Ruby is a proper noun here, not part of code fragment [ci skip]

Last line of note also relates heavily to first part
and parenthesis broke reading flow.
Merge pull request #13604 from randomecho/docs-getting-started

Ruby is a proper noun here, not part of code fragment [ci skip]
Require actionview/version

just like all the other modules do require their version file
Merge pull request #13607 from huoxito/actionview-version

Require actionview/version
update 4.1 release notes with deprecation commit link. [ci skip]
quick formatting pass through CHANGELOGS. [ci skip].
Fix typo in AMo docs [ci skip]
Merge pull request #13611 from robinboening/plugin_generator_tests

Add missing tests for invalid names in `rails plugin new` generator
Allow hyphenated names for `rails plugin new` generator.

It was not possible to create a new gem with a hyphenated name via the `rails plugin new` generator.

The naming guide of rubygems clearly says dashes should be used for gems that extend other gems. http://guides.rubygems.org/name-your-gem/