A basic tutorial instead of the demo mode

[dmitry_s]

I repurposed the demo level as a tutorial instead of the demo in the opening sequence and the demo mode that allows only to play 2 levels. The instructions so far are very basic.

The demo level is now a short but complete level instead of just a few rooms.

The first time the computer plays as prince. Then the player gets a chance to play the same level.

[atrueprincefanfrom18]

Wow, this is pretty cool!