Code refactoring - Watcher Decision Engine 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: Ie903ba20ca5cf03b0b42efa60131d1b919b0c2c9

watcher/tests/applier/framework/test_command_executor.py

@@ -22,7 +22,7 @@ from watcher.applier.framework.command_executor import CommandExecutor
 from watcher import objects
 
 from watcher.common import utils
-from watcher.decision_engine.framework.default_planner import Primitives
+from watcher.decision_engine.planner.default import Primitives
 from watcher.objects.action import Action
 from watcher.objects.action import Status
 from watcher.tests.db.base import DbTestCase

watcher/tests/applier/framework/test_command_mapper.py

@@ -19,7 +19,7 @@
 import mock
 from watcher.applier.framework.default_command_mapper import \
     DefaultCommandMapper
-from watcher.decision_engine.framework.default_planner import Primitives
+from watcher.decision_engine.planner.default import Primitives
 from watcher.tests import base