New version using QtQuick along with an experimental Map Background

Link ids were being used interchangeably with the mavlink channel for
the link. Link ids handed out as a numerically increasing integer. Once
the counter went past MAVLINK_COMM_NUM_BUFFERS all hell would break
loose and cause memory corruption.

Also removed partially implemented an incorrect getCommunicationStatus
api

Also many LinkManager API changes to further isolate all link
management inside LinkManager.

So this special casing is no longer needed

If it doesn’t exist it will be prefilled with all registered categories
set to false

Otherwise some messages say 'System MAV 0-20' and some say 'System 20'.

This signal passes the parameter type as well as param info

Removed "Clear Text" context menu from roll down dialog
Fixed "Clear Text" context menu in Info Dialog (renamed to "Clear Messages" in the process)

Shrunk the Message drop down dialog a bit.
Made the Message drop down dialog slightly transparent.

Moving methods from MainWindow to QGCApplication so that more things
can run without a window. Helpful for testing.

Emitting signal beforehand can lead to subtle bugs where code expects
value to be updated and it is not.

UASWaypointManager: don't clear systemid and compid of last partner so that we can still get DO_JUMP updates

UASWaypointManager: accept single waypoint messages in order to update the remaining DO_JUMP repetitions

Plus a large number of other changes to allow for orderly shutdown of
objects without crashes or asserts. This is need for unit tests to
create/delete global state around every test.