Major rework of rc subsystem

Implement channels mapping calibration.
Store mapping in parameters.
Get rid of `controls` array and store control inputs in `controlRoll`, `controlPitch`, ... variables.
Move `channels` variable to rc.ino, channels are not involved when controled using mavlink.
'Neutral' values are renamed to 'zero' - more precise naming.
`controlsTime` is renamed to `controlTime`.
Use unsigned values for channels.
Make channel values in simulation more alike to real world: unsigned values in range [1000, 2000].
Send RC_CHANNELS_RAW instead of RC_CHANNELS_SCALED via mavlink
Don't send channels data via mavlink if rc is not used

gazebo/simulator.cpp

@@ -71,11 +71,7 @@ public:
 		gyro = Vector(imu->AngularVelocity().X(), imu->AngularVelocity().Y(), imu->AngularVelocity().Z());
 		acc = this->accFilter.update(Vector(imu->LinearAcceleration().X(), imu->LinearAcceleration().Y(), imu->LinearAcceleration().Z()));
 
-		// read rc
 		readRC();
-		controls[modeChannel] = 1; // 0 acro, 1 stab
-		controls[armedChannel] = 1; // armed
-
 		estimate();
 
 		// correct yaw to the actual yaw