Update the user model to a single controller instead of multiple

Instead of hardcoded "QGroundContorl" strings

No more user prompting

Convert bool settings to SettingsFact

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

This prevents problems with toolbox references from inside
QGCTool::setToolbox calls.

Adding a dialog telling the user the map cache database has been reset.