Move config_accessor :asset_host from ActionController::Base to AbstractController which fixes issues with asset_host in ActionMailer

Including:
  - Moved mailer objects in separate directory
  - Added two tests for asset_host configuration option

[#4979 state:committed]
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Move Rails::LogSubscriber to ActiveSupport::LogSubscriber, allowing frameworks like ActiveRecord and ActiveResource to log outsude Rails::Application [#4816 state:resolved]

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

[#4843 state:resolved]
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

subject is automatically looked up on I18n using mailer_name and action_name as scope as in t('.subject')

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

[#4645 state:resolved]
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

[#4626 state:resolved]
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Changed encoding behaviour of mail, so updated tests in actionmailer and bumped mail version to 2.2.1
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Adding ability for the procs to be called within the instance, allows you to pass results from instance methods to the mail header
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

Mail::Part now no longer has nil as a default charset, it is always set to something, and defaults to UTF-8

Removing quoting.rb, upgrade to 2.1.3.6, changing all utf-8 references to UTF-8, updating tests where incorrect encoding

* Don't depend so much no the message in a NameError
* Reset the delivery method properly

Improve performance of the rendering stack by freezing formats as a sign that they shouldn't be further modified.

Finish cleaning up rendering stack from views and move assigns evaluation to controller (so plugins and/or controllers can overwrite just one method).

Fix a bunch of failing AP / AM specs created from the previous AbstractController configuration refactor.