Airdrop task - medium

[tedtasman]

Input: drop coordinate
Sends to AP: Mission w/ drop at coordinate

For an example of a task with params, look at the waypoint task.

This was somewhat implemented last year, for reference something like the following should go in compile:
https://github.com/tedtasman/MAVez/blob/5ea65ca0bd1fa2e7d8352b0568ae847a16aa1b75/flight_manger.py#L136