Add a cutscene, when entering the frontier plains the first time.

It's still missing a catchy image.
Fix objects in lost_mine1

Closes #338
Merge pull request #321 from stefanbeller/cutscene_alpha_demo

Add a cutscene, when entering the frontier plains the first time.
Merge pull request #343 from stefanbeller/mapfixes

Fix objects in lost_mine1
Fix height in menus/xp.txt

Closes #346
Fix typos in load game menu data
Merge pull request #348 from dorkster/typo

Fix typos in load game menu data
Merge pull request #347 from dorkster/menus

Fix height in menus/xp.txt