* Holds all the settings for the app
* Allows core plugin to override default values

Also added ui support for multiple complex item types

Prevent shutdown ordering crashes

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

Moving source files into Vehicles as it is a more coherent place.

Also change Plan Element selection ui

- GeoFence support comes from plugin
- Circle fence support
- Better param support