Bestlocation used when no GPS info their

maplen + distance calculator
- use only one Overlay for rendering which is a composite of two Tile- and Circle-Overlays
- simplify event logic, probably something broke along the way
- move Tile and Circle overlay to app
use MapTileLayer implementation
Merge branch 'lens_overlay' into tile_layer
- fix lens drawing multiple times
MapLens: fix initial position