Prevent shutdown ordering crashes

No need to add dynamic MockLink comm links

Retry in all the right/possible places. Don’t freak out about things
coming in unknown sequences.

Forcing QGC to use Mavlink V2 if vehicle supports it.

No signing support yet

_finalize methods need information which is not available if all you
have is a mavlink_message_t

This reverts commit ae976049ca7b4818616e6b8be07a028fc7dfc26f.

Also change Plan Element selection ui

* Add support for another board

* Added a 2nd custom board

- Now responds to request_list using a worker routine to send out
params one at a time
- Support for failure modes for unit testing