Feature DO_JUMP

This PR enables setting Waypoints of type DO_JUMP in QGroundControl to let a UAV cycle the waypoints forever.

Should resolve: #659

Tested in HIL, please review, thanks.

![hil do_jump](https://cloud.githubusercontent.com/assets/1419688/2658228/d0c9c3f6-c005-11e3-8361-49c1c44dcdd6.png)