First-cut of a refactored failsafe system.

* fixes issue where indicators would flash when SBus RX entered failsafe
mode.
* fixes bug where turning off a TX for an SBus RX would instantly disarm
when using a switch to arm when the channel went outside the arming
range.
* introduces failsafe phases to make the system more understandable.
* allows the system to ask if rxSignalIsBeing received for all RX
systems: PPM/PWM/SerialRX/MSP.  Also works when a serial data signal is
still being received but the data stream indicates a failsafe condition
- e.g.  SBus failsafe flags.
* failsafe settings are no-longer per-profile.

Untested: Sumd/Sumh/XBus/MSP (!)
Tested: SBus X8R, Lemon RX Sat, X8R in PWM, Spektrum PPM.

src/main/io/rc_controls.c

@@ -51,6 +51,7 @@
 
 #include "flight/pid.h"
 #include "flight/navigation.h"
+#include "flight/failsafe.h"
 
 #include "mw.h"
 
@@ -124,7 +125,8 @@ void processRcStickPositions(rxConfig_t *rxConfig, throttleStatus_e throttleStat
             }
         } else {
             // Disarming via ARM BOX
-            if (ARMING_FLAG(ARMED)) {
+
+            if (ARMING_FLAG(ARMED) && rxIsReceivingSignal() && !failsafeIsActive()  ) {
                 if (disarm_kill_switch) {
                     mwDisarm();
                 } else if (throttleStatus == THROTTLE_LOW) {