Level swithcing is now handled using level streaming

The new Base map loads all other maps, this way music can keep playing
while switching levels.
Added icons/splash images

-Added some key prompts on the HUD
-Countdown stops at 1
- Main menu matinee now stops before loading next level
I was not able to get the persistent level to stop all matinee inside
the seperate levels, so the matinee actor has been moved to the
persistent level.