added missing map thumbnails

added map preview images for Last Stand

- reorganized & simplified extras flyout menu

- updated to Rayman's Mutation Mod v52
- added support for new Quick Match flyout menu

- added missing mutation_mod.vtf thumbnail

- re-added custom gamesettings menus. hopefully didn't break them
- updated to latest mutation mod version v51

- update to latest Rayman's Mutation Mod
- fixes to main menu icons (removed single player / added vs survival)

v20.09.27
- update / fix for Last Stand dlc
- split screen mod removed

- back to normal version

- newyear mode for exit dialog activated