preliminary mapsforge support
try to fix tapping
"fix ocassional force-close in MapView" not needed for OSM

This reverts commit 12b6293ce7d824de309925c2ebc7275260599746.
mapsforge needs no gmaps
update code to mapsforge 0.3.0 API
replace old mapsforge lib with new version
Revert "map: wrap lat/lon requests into calls"

MapsForge API is incompatible, even though more efficient.

This reverts commit b1766bfa2e35e6ad9d240379d7f2895e6c03ca82.
OSM 0.3.0 needs SD write permission
OSM: query sdcard path
OSM: display error without map file
mapsforge: fix crash on Android 4.2

See also bug description and discussion:

http://code.google.com/p/mapsforge/issues/detail?id=370

https://groups.google.com/forum/?fromgroups=#!topic/mapsforge-dev/cGztCDPjwkI
OSM: map file chooser
OSM: allow more file pickers