Move Rails::Rack::Metal to Rails::Application::Metal and just add cascade if any metal was declared.

Conflicts:
	actionmailer/lib/action_mailer/base.rb

Fixed up being able to pass random headers in with headers, or mail.  Also, undeprecated headers(hash) as this works now too

Refactor railties test, break huge  files in smaller chunks and move initializers to application folder.

PostgreSQLAdapter: set time_zone to UTC when Base.default_timezone == :utc so that Postgres doesn't incorrectly offset-adjust values inserted into TIMESTAMP WITH TIME ZONE columns [#3777 state:resolved]

Conflicts:
	railties/test/railties/plugin_test.rb