* Add the Rack::Sendfile middleware
  * Make the header to use configurable via config.action_dispatch.x_sendfile_header (default to "X-Sendfile"). 
  * Add Railties tests to confirm that these work
  * Remove the :stream, :buffer_size, and :x_senfile default options to send_file
  * Change the log subscriber to always say "Sent file"
  * Add deprecation warnings for options that are now no-ops

Note that servers can configure this by setting X-Sendfile-Type. Hosting companies and those creating packages of servers specially designed for Rails applications are encouraged to specify this header so that this can work transparently.

Fix streaming by having it create a File object, which can be handled by Rack servers as appropriate

Add deprecation warning for calling filter_parameter_logging ActionController::Base, and allow it to be configured in config.filter_parameters
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Move filter_parameter_logging logic out of the controller and create ActionDispatch::ParametersFilter to handle parameter filteration instead. This will make filteration not depending on controller anymore.
Signed-off-by: NJosé Valim <jose.valim@gmail.com>