[WIP] Add export of KML

This is work in progress. Status on FF/Pale Moon
### Export from Drawing dialog
- [x] Points (including sizes)
- [x] Polylines (including coloring)
- [x] Polygons (including coloring)
- [ ] Text -> does not work

### Export from measure dialog
- [ ] All
There's a browser native function, but IE9 does not support it [1]. Maybe I can put this as a lib file an only load it on IE9 (like the angularIE9 fix). I'll give it a go.

[1] http://caniuse.com/#search=base64