Only make one call to get "movement_gravity" setting

heli_control.lua

@@ -1,6 +1,5 @@
 --global constants
 
-helicopter.gravity = tonumber(minetest.settings:get("movement_gravity") or 9.8)
 helicopter.tilting_speed = 1
 helicopter.tilting_max = 0.20
 helicopter.power_max = 15

heli_utilities.lua

@@ -1,4 +1,4 @@
-helicopter.gravity = tonumber(minetest.settings:get("movement_gravity") or 9.8)
+
 helicopter.vector_up = vector.new(0, 1, 0)
 
 function helicopter.get_hipotenuse_value(point1, point2)

settings.lua

@@ -1,4 +1,7 @@
 
+--- Determines gravity force on helicopter.
+helicopter.gravity = tonumber(minetest.settings:get("movement_gravity") or 9.8)
+
 --- Determines handling of punched helicopter.
 --
 --  If `false`, helicopter is destroyed. Otherwise, it is added to inventory.

settingtypes.txt

@@ -1,4 +1,7 @@
 
+# Determines gravity force on helicopter.
+movement_gravity (Movement gravity) float 9.8
+
 # If enabled, places helicopter in inventory instead of destroying it
 # when punched.
 helicopter.pick_up (Place in inventory) bool false