Replace 9 seperate valueChanged() signals with just 1, and remove the resultant tons of code duplication

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 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