Pushed HIL with X-plane to being close to operational. Receiving from X-Plane  implemented, sending to it is prepared. Needs an iteration of onboard SW first

Addressed issue #26. Select System, Plugins and System are disabled when neccessary. Removed style-outdoor-dark.css. Moved the other two .css files and Vera.ttf into files/styles.

Removed some dead code.
Added more valueChanged() signals to account for every data type. This moves the conversion over into the valueChanged receivers, which while it will require more slot-functions, makes it easier to add more code as any necessary conversion is done internally to the slot and so the signaler doesn't need to know the details.
I also added some more details on the types of units expected by valueChanged().

Fixed some destructor commands

Fixed roll angle in Google earth, still not smooth. Fixed a number of threading issues. Fixed all custom widget related bugs. Improved MAVLink decoder. Reduced CPU usage substantially across all views