Code refactoring - Watcher Applier package

This patchset is there to change the code structure.
The objective is to flatten the project file tree by merging
'api/' and 'framework/' into a single package. This also contains
some tidy ups in package naming (like using only singular nouns).

This should only affect file/folder names and their subsequent
import paths wherever they were used.

Change-Id: Id7b37667c613086d8ef3cd1f367c4219bf026fc7

watcher/api/controllers/v1/action_plan.py

@@ -28,7 +28,7 @@ from watcher.api.controllers import link
 from watcher.api.controllers.v1 import collection
 from watcher.api.controllers.v1 import types
 from watcher.api.controllers.v1 import utils as api_utils
-from watcher.applier.framework.rpcapi import ApplierAPI
+from watcher.applier.rpcapi import ApplierAPI
 from watcher.common import exception
 from watcher import objects