This is a major change to how we handle the scenario where a controller is
a filter. We want to change the lifetime of the controller object, by
scoping it around action filters and result filters. This means that a
controller class can only implement action filters and result filters.
To implement #384 - we're creating a delegating filter class
'ControllerFilter' which will forward calls to the implementation of the
controller. This is discovered in the controller model and added to the
filter collection. This filter is removable as an opt-out of this feature.
The ControllerFilter only implements action filter and result filter, so
the new restriction about filter types on Controller is in place. A future
change will move the instantiation of the controller to after resource
filters.
