Enable centered nodes by default

mods/doors/README.txt

@@ -132,7 +132,7 @@ Several fields of the definition table are required, but most are optional
  * def.sound_held_open - sound effect when trying to open a door in hold-open state
                          or when center door is blocked
  * def.sound_closing_mode - sound effect when changing door closing mode
- * def.can_center - whether center positioning (default is false)
+ * def.can_center - whether center positioning (default is true)
 
 For programmatically examining and manipulating doors, two API functions are provided:
 

mods/doors/api.lua

@@ -928,7 +928,7 @@ function doors.register_door( name, def )
 		def.can_offset = true
 	end
 	if def.can_center == nil then
-		def.can_center = false
+		def.can_center = true
 	end
 
 	if def.is_lockable == nil then