Replace DatapathConfig messages with RouteMod

Recent developments have introduced the RouteMod message type for sharing flow information between components in RouteFlow in a more general manner. This patchset takes this further by enabling RouteMod by default, and removes the superceded message types. This simplifies much of the codebase and also includes a fix for issue https://github.com/CPqD/RouteFlow/issues/27.

This does however break rfweb quite considerably (See issue https://github.com/CPqD/RouteFlow/issues/29).