add automatic map rotation

[Martin Kolman]

per ​http://talk.maemo.org/showpost.php?p=761988&postcount=18|request:

• rotate the map in the direction of travel -> direction of travel is on top

possible drawbacks:

• text orientation on tiled maps (aerial/sat tiles dont have text usually, so they should be OK)
• performance -> maybe use some sort of acceleration (OpenGL ES?)
• OPTIONAL: when the turn-by-turn navigation is active, move the position indicator down and show more of the map in the direction of travel