No signing support yet

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

Also change Plan Element selection ui

* Add support for another board

* Added a 2nd custom board

This mechanism automatically queues data into the correct thread where necessary, otherwise the method is invoked directly with low overhead.

At the same time remove the UDP socket event workaround. It is not a problem.

3DR Radios no longer exist

Plus other auto connect bug fixes

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

- Also fix vehicle selector dropdown in toolbar

This guarantees we are past bootloader on all OS. Window tends to not
detect bootloader, connect to it and then get confused.

Windows OS doesn’t disconnect port when you pull plug on USB. This
caused all sorts of problems with previous logic. New logic handles
this correctly.

- Pervasive change to automatically connect to known board types
- Lots of additional changes along with this:
- More exposure of objects/properties to Qml
- Much restructuring in LinkManager and LinkManager clients