SITL: add Gazebo SITL params for Iris with IRLocak tracking, Zephyr elevon flying wing model, and update sim_vehicles.py with GazeboIris and GazeboZephyr labels.

Try to make the various param files to follow similar namings:

    - Lowercase the few ones using uppercase
    - Use dash to separate name components
    - Start with "copter", "plane", "rover", etc instead of the mix we
      had
    - Remove "params" from the filename since it's redundant with the
      extension