DataFlash: added TERR log message for terrain data
AP_Terrain: added dataflash logging
Plane: use dataflash logging for terrain
AP_Mission: added last_change_time_ms() call

will be used by terrain lib for scanning waypoints
AP_Terrain: added automatic waypoint checking

check we have terrain data for all waypoints
AP_Rally: added last_change_time_ms() call
AP_Terrain: added automatic rally point checking
Plane: fix for changed AP_Terrain API
Copter: fix for changed AP_Terrain API
Plane: fixed typo in description
Rover: fixed build
VARTest: fixed build
AP_Rally: fixed build for non-standard vehicle types
CPUInfo: fixed build
AntennaTracker: fixed build
AP_Terrain: added missing TerrainMission.cpp
AP_Terrain: enable the terrain database by default

MissionPlanner now supports terrain data, and having terrain data in
logs is useful even if users don't fly terrain missions
AP_Terrain: don't request data at 0/0
Replay: fixed build
AP_TECS: added get_max_climbrate()