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/cli.ino

@@ -11,7 +11,7 @@ extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRO
 extern const int RAW, ACRO, STAB, AUTO;
 extern float t, dt, loopRate;
 extern uint16_t channels[16];
-extern float controlRoll, controlPitch, controlThrottle, controlYaw, controlMode;
+extern float controlTime;
 extern int mode;
 extern bool armed;
 
@@ -132,6 +132,7 @@ void doCommand(String str, bool echo = false) {
 		}
 		print("\nroll: %g pitch: %g yaw: %g throttle: %g mode: %g\n",
 			controlRoll, controlPitch, controlYaw, controlThrottle, controlMode);
+		print("time: %.1f\n", controlTime);
 		print("mode: %s\n", getModeName());
 		print("armed: %d\n", armed);
 	} else if (command == "wifi") {