Map marker and annotation bugfixes

Description

This fixes several bugs in map annotations:

1. It anchors map pins at the bottom (they appear to "point to" the location being marked, instead of being centered over it)
2. It forces the "My Location" marker to always be shown
3. It forces the map pins to always be shown (below the my location marker, in the case of overlap)
4. It forces the icons on the favorites layer to be shown unless selected with a map marker, below other layers in the case of overlap.