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
add highlight point and color property to the track type
draw highlighted point with highlight color
extend the clickable_track example to also highlight the clicked point
use the correct alpha variable