Code style cleanups

Add keyword arguments. Sort arguments and models.
Move literals to their own module. Prepend handler_ to
signal handlers.

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

mayan/apps/documents/models/misc_models.py

@@ -1,8 +1,6 @@
 from __future__ import absolute_import, unicode_literals
 
-import hashlib
 import logging
-import uuid
 
 from django.conf import settings
 from django.db import models
@@ -23,15 +21,6 @@ __all__ = (
 logger = logging.getLogger(__name__)
 
 
-# document image cache name hash function
-def hash_function():
-    return hashlib.sha256()
-
-
-def UUID_FUNCTION(*args, **kwargs):
-    return force_text(uuid.uuid4())
-
-
 class DeletedDocument(Document):
     objects = TrashCanManager()