Toggling between maps for multiple cultural / environmental variables, map is downloadable (sort of?)

Fix for #168 , #45 in progress

Current position of legend will be changed.

The map is downloadable, however, at the moment users need to visit the map tab before the map download link is appended to the 'downloads' list.  At the moment, if multiple traits are selected, the relevant map downloads are appended to the 'downloads' list one by one as they are selected.  This was just quick code to see if I could get it working.

- What to display for society markers on society results table?  
- Still need to add a legend for environmental variables

This can easily undo itself since it's just swapping the coordinates every time the collection changes.
I'd prefer to keep the reverse() where it was. I probably should have documented that better - jVectorMap expects (Lat, Lon) but GeoDjango models use (Lon, Lat)