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/linking/serializers.py

@@ -6,8 +6,10 @@ from rest_framework import serializers
 from rest_framework.exceptions import ValidationError
 from rest_framework.reverse import reverse
 
-from documents.models import DocumentType
-from documents.serializers import DocumentSerializer, DocumentTypeSerializer
+from mayan.apps.documents.models import DocumentType
+from mayan.apps.documents.serializers import (
+    DocumentSerializer, DocumentTypeSerializer
+)
 
 from .models import SmartLink, SmartLinkCondition