Caching: Turn the new caching into its own app

Extract the new smart file caching code from the common app
and convert it into its own new app called file_caching.

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/documents/models/document_version_models.py

@@ -112,7 +112,7 @@ class DocumentVersion(models.Model):
 
     @cached_property
     def cache(self):
-        Cache = apps.get_model(app_label='common', model_name='Cache')
+        Cache = apps.get_model(app_label='file_caching', model_name='Cache')
         return Cache.objects.get(name=DOCUMENT_IMAGES_CACHE_NAME)
 
     @cached_property