Switch to full app paths

Instead of inserting the path of the apps into the Python app,
the apps are now referenced by their full import path.

This solves name clashes with external or native Python libraries.
Example: Mayan statistics app vs. Python new statistics library.

Every app reference is now prepended with 'mayan.apps'.

Existing config.yml files need to be updated manually.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/task_manager/tests/test_views.py

@@ -1,6 +1,6 @@
 from __future__ import unicode_literals
 
-from common.tests import GenericViewTestCase
+from mayan.apps.common.tests import GenericViewTestCase
 
 from ..classes import CeleryQueue
 from ..permissions import permission_task_view