Merge pull request #31 from smartyg/editable-modifications

Editable modifications
change drag and drop to the right mouse button
add clickable property to OsmGpsMapTrack
add point-selected signal to OsmGpsMapTrack
make tracks with property clickable clickable with the left mouse button
add clickable_track example to give a simple idea of the use of clickable/selectable points
update example: there is no point user data in this branch, add 2 more points and free points properly.
fix whitespaces
fix whitespaces
typo
fix: dont copy point when passed by signal, sent the pointer to the original point to the callback
fix whitespaces
fix comment