Some initial work for #601.
Merge branch 'master' of https://github.com/GeoNode/geonode into issue-601
Now it is possible to display a layer style in the map.
Removed some sample xml from comments.
Merge branch 'master' of https://github.com/GeoNode/geonode into issue-601
Now it is possible to download styles from layer info page.
Refactored some code as there was an unassigned reference.
Updated the fixtures with the default_style fk value for the test layer.
add reference api-doc for models, sphinx plugin
Merge pull request #859 from ischneider/api-doc

add reference api-doc for models, sphinx plugin
Merge pull request #849 from capooti/issue-601

GN database is now synced with layer style information, refs #601
Moved the layer styles deletion logic from the view to the model's signals.
Adding a default title for style.
Added some test for the style stuff.