Split constructor of HeartbeatTimer up in two functions

Previously the first activeChanged signal got lost because it was not connected yet to the LinkInterface which resulted in a link incorrectly shown as inactive.

Fix for vehicle widget bug

Ignoring Jenkins (Linux) 

Making sure the commands are sent to the camera's actual component ID rather than a hardcoded constant.

QGCFileDialog: Specify fully qualified in folder url

Expose VideoReceiver allowing plugins to override it.

Plan, Offline Maps: Support for center map to specified location

PreFlight: Reorganize to retain state

Vehicle recenter takes into account correct viewport

ArduCopter Tuning - Remove Hover Throttle from tuning

Various fixes

ArduCopter: Initial Heli Setup page

Windows Appveyor: Switch to Qt 5.11

Fix compiler warning

Also distinguish Emergency Stop better

This was too confusion to expose since QGC currently does not support ArduPilot terrain tile send.

Stable merge: Pull was missing from Stable->master

Even more PreFlight reorg/support

More PreFlight control reorganization