Small Action View Overview edits [ci skip]

Some small grammar and readability edits
Define the Duration#instance_of? method

Since Duration is extending from ProxyObject which extends itself from
BasicObject, the Duration object doesn't respond to the #instance_of?
method. Thus, the #method_missing hook get triggered, delegating the
method to its `value` attribute.

However, Rubinius' #eql? definition relies on #instance_of?, thus this
will equal to true with a Fixnum (since its `value` attribute is a
Fixnum) while it should not.

The previous behavior was wrong anyway, no matter the implementation.
Grammar pass

[ci skip]

Add improvements from @eileencodes [skip ci]
Added enqueue_at support for QueAdapter in ActiveJob

* Added inline job runner for Que in test/support
* Updated QueAdapter to support enqueue_at
[ci skip] Clarify Action Mailer/Active Job usage note
Merge pull request #16612 from loganhasson/master

[ci skip] Clarify Action Mailer/Active Job usage note
Make text consistent in help text of rails server and console commands.
Guide fix. [CI SKIP]

Related: https://github.com/rails/rails/pull/16607
adding the exception RecordNotFound to UUID find
[ci skip] Added documentation for has_one scope parameter
Merge pull request #16615 from tgxworld/guide_fix

[ci skip] Grammar fixes for upgrade guide from 4.0 to 4.1
Merge pull request #16617 from tomkadwill/added_has_one_scope_documentation

[ci skip] Added documentation for has_one scope parameter
Merge pull request #16204 from jonatack/patch-7

Fix minor typos and improve grammar and code formatting
Merge pull request #16271 from alol/action-view-overview-guide-tweaks

Small Action View Overview guide grammar and readability tweaks
Add change to ActionView Notable changes [ci skip]
Merge pull request #16621 from Calyhre/patch-1

Update documentation, Add change to ActionView Notable changes
Don't fight against ourselves for the default log level

If we want to always default to :debug, let's just do that.

At which point the production.rb entry can become an "uncomment to
change" instead.
applies API guidelines to new AM docs
ActiveJob -> Active Job [ci skip]

See http://guides.rubyonrails.org/api_documentation_guidelines.html#wording
Refactor ActionDispatch::RemoteIp

Refactored IP address checking in ActionDispatch::RemoteIp to rely on
the IPAddr class instead of the unwieldly regular expression to match
IP addresses. This commit keeps the same api but allows users to pass
IPAddr objects to config.action_dispatch.trusted_proxies in addition
to passing strings and regular expressions.

Example:

    # config/environments/production.rb
    config.action_dispatch.trusted_proxies = IPAddr.new('4.8.15.0/16')