refactor!: globals (#717)

* refactor(globals): use macro's for to_json/from_json
* refactor(globals): switch from global pointer to global instance

src/backend/backend.cpp

@@ -13,7 +13,6 @@ namespace big
 
 		while (g_running) 
 		{
-			g->attempt_save();
 			looped::system_self_globals();
 			looped::system_update_pointers();
 			looped::system_desync_kick_protection();