Copter: add AUTOTUNE_AXES bitmask parameter

This is used to allow tuning just some axis

ArduCopter/Parameters.h

@@ -315,6 +315,7 @@ public:
         k_param_acro_balance_roll,
         k_param_acro_balance_pitch,
         k_param_acro_yaw_p, // 244
+        k_param_autotune_axis_bitmask,  // 245
 
         // 254,255: reserved
     };
@@ -462,6 +463,9 @@ public:
     AC_P                    p_stabilize_yaw;
     AC_P                    p_alt_hold;
 
+    // Autotune
+    AP_Int8                 autotune_axis_bitmask;
+
     // Note: keep initializers here in the same order as they are declared
     // above.
     Parameters() :

ArduCopter/Parameters.pde

@@ -1037,6 +1037,13 @@ const AP_Param::Info var_info[] PROGMEM = {
     GOBJECT(optflow,   "FLOW", OpticalFlow),
 #endif
 
+    // @Param: AUTOTUNE_AXIS_BITMASK
+    // @DisplayName: Autotune axis bitmask
+    // @Description: 1-byte bitmap of axes to autotune
+    // @Values: 7:All,1:Roll,2:Pitch,4:Yaw,0:None
+    // @User: Standard
+    GSCALAR(autotune_axis_bitmask, "AUTOTUNE_AXES", 7),  // AUTOTUNE_AXIS_BITMASK_DEFAULT
+
     AP_VAREND
 };