Better api for enabling features by default

Removed the static way to disable features

Removed the static Feature.Enable

Removed the is enabled static

Removing the feature category concept

Adjustments after pairing with Cameron.

Getting the selection if serializer working again
Making sure that dependencies are honored
Moving GetConfigSection onto the settings holder
Configuration source is now required to be specified up front to avoid
ordering issues
Better config builder api and removed the raven tests since they got in
the way. (they are beeing moved to a external repo anyway)
Endpoint name is now moved to the config builder to avoid issues with
ordering. Raven also removed from the core
Removing the dispatcher factory abstraction since the pipeline now convers
it
Removing the ConfigUnicastBus
Making sure we call onCritical error on a separate thread to avoid dead
locks
Fixed an issue with the retries queue not beeing created
More feature api improvements
Improved the configure.Features api
Api doco for the features
Fixed a bug in the gateway registration
Merge pull request #2129 from Particular/new-feature-api

New feature api