Bump Django.
Include uploaded file in paver reset
Simplified handling of thumbnails.

* Added tests for thumbnails in Layers and Maps.
* Removed ThumbnailMixin class and just created methods in ResourceBase.
* Removed need to call save again in catalogue or mess with signals.
* Added logic to return the link to the WMS image in thumbnail if WMS is not yet available during upload.
* Uploads are now around 2x faster.
Fixed map saving.
Missing imports
Pass in the style name as a string vs an object when settings styles on layers.  Fixes #1456.
Fix typo'postigs'

Fixes #1459.
Fixes #1458
Add geoserver context to the layer detail view and add the store_type helper.