pymavlink: raise version
common.xml: added MAV_SYS_STATUS_TERRAIN
common.xml: added MAV_CMD_PREFLIGHT_SET_SENSOR_OFFSETS for 2nd magnetometer
ardupilotmega.xml: merged latest changes from ardupilot git
XML: resolved conflicts between APM and PX4 MAV_CMD_* messages

as discussed with Lorenz and Randy
Fix docs in XML on quaternions
Fix conversion docs in C
common.xml: added MAV_FRAME_GLOBAL_TERRAIN_ALT
pymavlink: added support for terrain altitude mission creation
pymavlink: raise version
common.xml: added current height above the location to TERRAIN_REPORT

this is a very useful piece of information in the TERRAIN_REPORT, and
should be displayed on GCS status page
pymavlink: raise version
pixhawk.xml: added detection stats message
pixhawk.xml: added a health message for the onboard computer
Removed protobuf hack
Merge pull request #221 from swissfang/obcadditions

pixhawk.xml: added detection stats message
pixhawk:xml: adapted stats and health messages after discussion
pymavlink: added insert() method to mavwp
Merge pull request #222 from swissfang/obcadditions2

pixhawk:xml: adapted stats and health messages after discussion
mavgen: generate full enum information

this enables introspection to tell is a MAV_CMD has a location, plus
what parameters it takes