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
Small fixes to thumbnails.

* Return the .url property vs the layer object.
* The geoserver pre-save signal should user filter vs get to lookup thumbnails.
* Add missing gs_uploader import to the upload models.
Refactor the last commit to fix broken tests.
Moves geoserver-specific url routes to the geoserver app.

* acls, resolve_user and layer_batch_download have been moved to /gs/acls, gs/resolve_user, and gs/download.
* The old routes (using the /layer prefix) still work, but should be removed once legacy code is updated.
Remove the duplicate forward slash from the gs/rest/layers url route. Fixes #1457.
Merge pull request #1460 from garnertb/gs-layer-views

Moves geoserver-specific url routes to the geoserver app.
Tidying while reading

Avoid deep indentation, use more levels of headings instead.
Some more doc tweaks
Tidying while reading

Indentation fixed on one section too.