Replaced the autopilot-specific inclusion of MAVLink to be more generic. Now if you have no actual QGC modifications to make and just want your messages to be available for viewing/logging you can just create the user_config.pri file and override MAVLINK_CONF.

Modified SerialLink.cc so that it follows the same cross-platform restrictions as the QSerialPort library it relies on.
Windows compilation was broken during 94e91013, which is what prompted this refactoring.

Introduced persistence in RGBDview, needs debugging, fixed a bug in param reading in the simulator, pushed message sender a bit forward, not working yet

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

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.

Enabled visualization of point cloud data via Protocol Buffers serialization and extended_mavlink_message.

Minor cleanup, fixed a bug where the serial port would not connect on first application launch on Linux