Throttle trim must be center throttle

Since parameter system will pop message based on meta data

Refactored PX4 radio config to work with both PX4 and APM

- MultiVehicleManager is a Qml friendly replacement for UASManager
- Vehicle is a replacement for both UAS and AutoPilotPlugin

Also:
- Prompts to reset trims to zero prior to calibrate
- Turned of radio check for now since it prevents spectrum bind

QGCUASParamManager and friends are replaced by FactSystem

This way live rc update is correct after a calibrate

- All resources are either under src or under resources dirs
- Removed files top level directory
- Move flightgear files to top level dir

Also converted to new logging category

Subclass of QMessageBox which re-implements the static public
functions. There are two reasons for this:
1) The QMessageBox implementation on OSX does now show the title
string. This leads to message boxes which don't make much sense. So on
OSX we set title to text and text to informative text.
2) If parent is NULL, we set parent to MainWindow::instance. This
prevents message boxes which can go behind MainWindow