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/document_indexing/licenses.py

@@ -1,6 +1,6 @@
 from __future__ import absolute_import, unicode_literals
 
-from common.classes import Package
+from mayan.apps.common.classes import Package
 
 Package(label='Django MPTT', license_text='''
 Django MPTT