Refactor arming logic

Arm and disarm with gestures only: left stick right/down for arming, left/down for disarming.
Remove arming switch as it complicates arming gestures logic.
Remove MAV_CTRL_SCALE parameter as it complicates arming gestures logic, advise to decrease TILT_MAX when controlling with a smartphone.
Put some minimal thrust to motors to indicate armed state.
Rename build article to usage article, add flight instructions.

flix/parameters.ino

@@ -70,12 +70,7 @@ Parameter parameters[] = {
 	{"RC_PITCH", &pitchChannel},
 	{"RC_THROTTLE", &throttleChannel},
 	{"RC_YAW", &yawChannel},
-	{"RC_ARMED", &armedChannel},
 	{"RC_MODE", &modeChannel},
-#if WIFI_ENABLED
-	// MAVLink
-	{"MAV_CTRL_SCALE", &mavlinkControlScale},
-#endif
 };
 
 void setupParameters() {