Added dirty implementation of "render_model_details" templatetag.
Added new templatetag library "avatar" which adds support to gravatars.
Added details view for "User" model.
Fixed issue with kwargs in "ModelListFilteringMixin".
Removed subtitle in "base_detail" template.
Added tests for "render_model_details" templatetag.
Fixed issue on deleting user-related bookmarks.
"ObjectPermissionBackend" is now more user model agnostic.
Fixed issue with signals management in "core" app.
Fixed dashboard deletion on owner deletion.
Added tests to verify correct deletion of bookmarks and dashboards.
Removed Django's "contrib.comments" and "contrib.markup" deprecated apps.