Move all global variable declarations to the appropriate subsystems

As it makes the subsystems code easier to understand.
Declare the most used variables in main sketch file as forward declarations.
Make all control input zero by default (except controlMode).
Minor changes.

flix/vector.h

@@ -35,7 +35,6 @@ public:
 		z = NAN;
 	}
 
-
 	float norm() const {
 		return sqrt(x * x + y * y + z * z);
 	}