New main menu WIP
Main menu WIP #2
Finish main menu redesign + Replace Minetest with Freeminer in few places.
Merge branch 'mainmenu'

Conflicts:
	README.txt
	builtin/mainmenu.lua
	builtin/modmgr.lua
	src/defaultsettings.cpp
Fix shaders settings.
Merge pull request #3 from xyzz/mainmenu

Mainmenu