Add estimator selection logic to VTOL apps

ROMFS/px4fmu_common/init.d/rc.vtol_apps

@@ -4,9 +4,22 @@
 # att & pos estimator, att & pos control.
 #
 
-attitude_estimator_q start
-#ekf_att_pos_estimator start
-position_estimator_inav start
+# The system is defaulting to INAV_ENABLED = 1
+# but users can alternatively try the EKF-based
+# filter by setting INAV_ENABLED = 0
+if param compare INAV_ENABLED 1
+then
+	attitude_estimator_q start
+	position_estimator_inav start
+else
+	if param compare LPE_ENABLED 1
+	then
+		attitude_estimator_q start
+		local_position_estimator start
+	else
+		ekf2 start
+	fi
+fi
 
 vtol_att_control start
 mc_att_control start