* remove non-functional gazebo headless arg
* remove unused namespace args
* simplify mavros launch, use mavros's px4.launch instead
* fix single_vehicle_spawn spelling
* formatting with xmllint: remove empty lines, set intent to 4 spaces, add xml tag for editors, add comments to break up spections
* remove old and deprecated launch files
* add respawn_gazebo arg to be used with empty_world.launch
* catch rospy sleep method's exceptions
* fix copy-paste mistake in land state failure message
* add more logging to help with #8556
* log subscribed topics on mission start and test exit (pass or fail)
* use mavlink enums everywhere to avoid maintaining dictionary mappings and to have readable values
* log when the FCU advances to next mission item without satisfying the position reached offset/radius
* some renaming for readability
* log more state value changes (connected and MAV_STATUS)
-created a test base class to centralize redundant methods among the different tests
-added mission waypoint list topic listener (this also helps make sure the simulation is ready)
-check number of mission waypoints in FCU against mission
-increase time for mavros topics to be ready from 30 to 60 seconds
-reduce position check loop rates
-clean up logging
-support QGC plan for mission file format, see #8619
-vehicle is an arg for mission test launch file, working toward other airframes
-Jenkins: fix vtol vehicle arg value
-get MAV_TYPE param and use FW radius for pure fixed-wing mission position check
-remove unused vehicle arg from test in multiple tests launch, clearing runtime warning
two xml log files are generated for each rostest. they're named according to the launch file, which is reused for each mission test. currently subsequent tests overwrite the previous test's logs. this renames them after they're generated, appending the mission name to the end of the file name.