Issue #18

Fixed #18 by
- moving CustomMainMenu files into „Game“
- Set up „BasicMainMenu“ Class as engine’s core
- Added „launch“ method in WEMain.
- changed custom main menu a bit (not real part of engine)

Instead of starting with the game controller and view by yourself you
just add a BasicMainMenu screen and the rest is up to the game
programmer.
Merge branch 'issue-#18' into 1.2