Add SERVO disable field (betaflight#800)

Author: haslinghuis

src/flightlog.js

@@ -1773,6 +1773,7 @@ FlightLog.prototype.isFieldDisabled = function () {
     disabledFieldsFlags.GPS = (disabledFields & (1 << 12)) !== 0;
     disabledFieldsFlags.RPM = (disabledFields & (1 << 13)) !== 0;
     disabledFieldsFlags.GYROUNFILT = (disabledFields & (1 << 14)) !== 0;
+    disabledFieldsFlags.SERVO = (disabledFields & (1 << 15)) !== 0;
   }
 
   return disabledFieldsFlags;