Working on cleanup so that I can understand what's happening...
WIP
Start of tiny bit of documentation
Remove obsolete AhnIndex model from admin.py
Fixes to make things work; Landuse translator Excel file; start of augmented URLs for GeoImages so that maybe we can make them depend on the scenario (but maybe that won't be necessary)
Migration from custom grids
Make sure that if a custom landuse dataset is used, the original one is still placed in the tile cache
Add comment
Add tests, move some functions to tiles.py
- Save custom landuse map in a GeoImage, use only the scenario's
  landuse map slug for the landuse KML if a custom map was uploaded
  (so not tiled in that case).
Rearrange impots
Send email if an exception occurs in a task (one to the user,
one with a traceback to the servicedesk).
WIP
Make sure path is a bytestring when using gdal.Open(path)
Call GetField on a feature explicitly, for the older GDAL on the staging task server
Correct function name
Dataset must be opened
Store files in /media/
Move gdal_open to models, use it there
Move some email sending into emails.py