eWLD: add mine map

[ErwinKomen]

RvH: Add a map to view the mijn locations instead of the dialect locations.

[ErwinKomen]

Strategy

1. Use a list with the coordinates of the mines (RvH)
2. Coordinate incorporation
   1. Option: add a table linking between Mijn and Coordinate
   2. Option: add a field to table Mijn with the coordinate
3. Front-end: there already is a 'map' symbol in the 'description' part of the Lemma search result view
   1. Add another 'map' symbol (different color? different shape?) to get a mijnen-map-view
4. The mijnen-map-view shows (a) for one lemma, (b) all mijn-locations where each of the trefwoord variants is used
   1. Note that this is very similar to the already existing Lemma-trefwoord-map-view

[ErwinKomen]

Implementation

1. Models
   1. Add a field point to class Mijn - done
   2. Update database - done
2. Import the mine coordinates
   1. Convert from hms to decimals - done
   2. Copy paste to database - done
   3. Adapt the admin.py to facilitate the mines - done
3. Front-end
   1. Add a mine symbol next to the 'map' symbol in the 'description' part of the Lemma search result view
   2. No, doesn't work. It has become a map symbol, but in a different color
4. View
   1. Add 'lemmaminemap' as view LemmaMineMapView

[ErwinKomen]

Seems to work now.