Fixed adapt_controllers.py to allow plugging app on deep paths

You can now pass dotted mount path (Ex. "api.messages") to mount your pluggable apps in a deep path.
If an intermediate path is missing (Ex. "api.resources.messages" and /api/resources doesn't exists), it will raise an error when plugged, stopping the application launch.
If a controller is already mounted at the specified path, the route will be overwritten.