Add a game version selection system

+ Add GameVersion
+ Add Configuration
+ Add GameVersionForm
Position GameVersionForm in the center of the screen
Rename T3 Entry to Scenery Entry
Add OldSceneryEntry for Crash 1
Move general 3D code from EntityEntryViewer to a new base class

+ Add IPosition
+ Implement IPosition in EntityPosition
Add a renderer for Old Scenery Entries

+ Add OldSceneryVertex
+ Add OldSceneryPolygon
+ Add OldSceneryEntryViewer