Make the marker flicker less

Only redraw it if the position actually changed.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Don't always center the map on the marker

By default this is on, but there's a button that toggles the behavior. Also, if
the user drags the map then centering immediately stops (otherwise the user
fights a losing fight against the centering function).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Merge pull request #56 from dirkhh/mapImprovements

Map improvements