Remove duplicated url_for code and move methods shared between ActionMailer and ActionController up to AbstractController.

  * Move #set_cookie and #delete_cookie inline to optimize. These optimizations should
    almost certainly be sent back upstream to Rack. The optimization involves using
    an ivar for cookies instead of indexing into the headers each time.
  * Was able to use a bare Hash for headers now that cookies have their own joining
    semantics (some code assumed that the raw cookies were an Array).
  * Cache blankness of body on body=
  * Improve expand_cache_key for Arrays of a single element (common in our case)
  * Use a simple layout condition check unless conditions are used
  * Cache visible actions
  * Lazily load the UrlRewriter
  * Make etag an ivar that is set on prepare!

Break up DependencyModule's dual function of providing a "depend_on" DSL and "included" block DSL into separate modules. But, unify both approaches under AS::Concern.

This reverts commit 0cac68d3.

  * Removing the dependency on AD::Request and AD::Response
  * Moving the logic for the request and response object
    into a new module that is included by default.
  * Changing Renderer and Redirector to use self.headers,
    self.content_type, and self.status, which have very basic
    default implementations on AC::Http. When RackConvenience
    is included (which it is by default on AC::Base), the full
    Request/Response logic is used instead of the simple logic.

This reverts commit a747ab5b.