Fix mad merge

Adjust merge to Stable code

Support up to 64 buttons, not limit to 16
Send a single button command and not a stream of commands at 25Hz
Send button commands through signals (it's coming from a different thread)
Hide gimbal support through analog channels (there are no MAVLink messages to handle it)

FMUK66 updates

Map gimbal controls
Keep track of gimbal position within Vehicle

Add gimbal to external control signal

Add camera trigger
Add video start/stop/toggle recording
Add gimbal pitch and yaw

Add .apj file picker support

With the switch to QtQuick, all file dialogs from the c++ side no longer work. This was marked as TODO and fell through the cracks.

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Restored FirmwareUpgrade.qml as it was beyond repair. Also fixed some issues that were present in the original, master version.
Added "hasAPMSupport" to QGroundControl global control. This is to determine if APM support is enabled or not.

Handle fmuv2/v3

Don't hideDialog when it doesn't flash

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Switch to using firmware manifest for ArduPilot flashing