Update: added 'resolution control' button to avoid flashes during level change

Hi guys, I've updated a little change that hopefully will be considered useful. Since an user (thanks SooFany for the heads-up) experienced flashes during level change, I added a button in System options page, that turns off/on control of video risolution by the engine.

Setting it to on, it'll avoid to refresh current resolution every level change, and those flashes should be gone. Instead, the screen will go white until it loads all the contents of the level and it will then present the actual graphics of the game. If you should experience some issues, you can just turn it off and let me know in the community pages.