Fixing the telemetry RSSI indicator.

For showTouchAreas and showAdvancedUI

Removing dead weight. This entire controller should be removed and the functionality moved to Vehicle.

Other minor formatting and stability improvements

* Make MainToolbarIndicators reusable by other views
* Change to font based ratio sizing

* Vehicle selection must be global control
* Disconnect controls must be associated with Vehicle

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

Also removed intermediate param load retry message

Also added new FirmwarePlugin::brandImage support