sim_vehicle.py: choose default waf_target based on specified vehicle
sim_vehicle.py: add --no-rebuild-on-failure option
sim_vehicle.py: make help clearer by adding option groups
sim_vehicle.py: improve output of executed commands
Emit something that could be copy-and-pasted into a shell
sim_vehicle.py: allow specification of multiple gdb breakpoints
sim_vehicle.py: understand some specific mavproxy options
sim_vehicle.py: validate vehicle, throw warning if it looks suspect
sim_vehicle.py: avoid use of psutil (cygwin not supported)
sim_vehicle.py: rename build_target to make_target
sim_vehicle.py: pass vehicle binary to start_vehicle
sim_vehicle.py: waf build system support
sim_vehicle.py: use waf by default