LinkInterface and Vehicle uses mutexes to synchronize writing bytes to the link instead of queued signals

Rework handling of fw/vehicle type with respect to conflicts with actual vehicle types.

App messages now use simple modal message dialogs. Vehicle messages continue to use non-modal popup.

Remove unnecessary includes of QGroundCotrolQmlGlobal.h

qobject_cast is times faster dynamic_cast for objects that
inherit QObject. also, use auto keyword to not duplicate
class names.

Add the HeartbeatTimer class to track a single heartbeat for a single link.
For every new received heartbeat an instance of the class is created.
Every instance emits a signal if it timed out or the timer is restarted.
Each vehicle then decides based on all different signals which link is the
priority link.

* Flight modes still not implemented. Waiting on message change.
* Also includes various cauterization of UI things which should not be
available on high latency link.

This extension introduces a complete version handshake mechanism which will detect wether the vehicle AND the complete link / routing infrastructure support MAVLink 2. If they do, QGC will switch to the highest protocol version supported by all connected vehicles. If a new vehicle connects, it will re-negotiate the highest possible version. This means that we error on the side of compatibility, which later can be easily changed.

Remove/comment off debug output pollution

Instead of hardcoded "QGroundContorl" strings

* Holds all the settings for the app
* Allows core plugin to override default values

Use component id from heartbeat

Prevent shutdown ordering crashes

Made QGCCorePlugin derive from QGCToolBox and expose everything through the same mechanism as everything else.

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

Includes ability to load params

Temporarily disable MAVLink version check as the QGC settings have no effect and it will mess with the upgrade from v1 to v2 and has no real value