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