Improve the waypoint context menus. Now it's possible to delete and duplicate comple...

Improve the waypoint context menus.  Now it's possible to delete and duplicate complete trees of waypoints at once.  The 'change interp' functionality has been extended too, so now it's possible to set the interpolation type for the whole waypoint from the context menu as well as just the side that was clicked on, and it's possible for single waypoints as well.

git-svn-id: http://svn.voria.com/code@1584 1f10aa63-cdf2-0310-b900-c93c546f37ac