Drop Waypoint Handling #15

Handle drop waypoints.

• Store a list of drop waypoints from Drop Waypoints GroundStation#150, with file backups for safety
  • Each waypoint contains a waypoint number (correlating with the PixHawk) and the bottle number to drop
• Create an async thread that checks whether the plane is going towards a drop waypoint, and save this as a flag
• When the plane switches waypoints (and is now going towards the waypoint after a drop waypoint), drop
  • Actuate the drop mechanism corresponding to the specified bottle, as soon as possible
• An additional feature would be sending the drop command a bit earlier, to account for processing and mechanical delays