Tidy up - Primitive

Some Python class and packages need to be renamed
for a better compliance with the shared terminology
which provides a better understanding of Watcher
objects and components by every contributor.

This patchset is there to change
Primitive to Primitives.
Add BasePrimitive.

Partially implements: blueprint glossary-related-refactoring

Change-Id: I839bddd12b5320b338b2f207d74963afa23de522

watcher/tests/applier/actions/wrapper/test_nova_wrapper.py

@@ -18,7 +18,7 @@
 #
 import mock
 import time
-from watcher.applier.primitive.wrapper.nova_wrapper import NovaWrapper
+from watcher.applier.primitives.wrapper.nova_wrapper import NovaWrapper
 from watcher.common import utils
 from watcher.tests import base