cause: check for null pointer had no effect (static memory)
solution: fill mavlink messages (and thus) message type with 0xff. this patch assumes that message ID 0xff is never used
positiv side effect: qgroundcontrol uses 2% less cpu on my machine (eeepc)

sending GPS sat information via a low-bandwidth link like the UM96 @ 9600 baud should also work at low frequencies like 0.2 Hz

Changed the drop rate from a SYS_STATUS message to follow the MAVLink specs along with some extra range checking.

Added a workaround to the mission management code where it would only accept messages addressed to the MAV_ID_MISSIONPLANNER component. This was causing problems with the send-loss value being calculated, so I decided to add this until a proper solution can be developed.

Refactored part of MAVLinkProtocol::receiveBytes() as I was trying to debug within it. Nothing major, though I did remove an unnecessary loop.

Added multi-UAS support to QGCRGBDView. Fixed display timeout issue on computer for which data source is not time-synchronized.

Code changes to reflect new header information (sysid, compid, timestamp) in protobuf messages. Added protobuf message timeout; old messages will not be visualized. Fixed getParameterValue in ParamManager; the method can segfault if the component id or parameter id is not valid.

Also removed redundant code in QGCMapWidget.cc.

Added support for reading uint8 values from an autopilot via QGC. Still need to add support for writing them.

Also reorganized the code to be more readable.

Some more bugfixes and improvements for the Mission Plan widget. The "current"-checkbox in "Onboard"-waypoints can no longer be changed by clicking directly, but it is handled internally by QGC. Now there should be one and only one checked checkbox, which shows the last KNOWN "current" waypoint on MAV. The white border around an unchecked checkbox means, that the user is requesting the change of current waypoint, but QGC has not received MISSION_CURRENT message as a confirmation yet. Also,if there is no response from UAV after pushing "Read" or "Refresh", the "Onboard" list will be deleted to indicate, that there is no information available.