Allow OldSceneryEntryViewer to display multiple entries
Add a basic implementation of IPosition
Use OldSceneryEntry x/y/z offsets in OldSceneryEntryViewer

+ Add x/y/z offset properties to OldSceneryEntry
Identify f0-3 as rgb components in OldSceneryVertex
Fix the scale of old scenery code (was 8x too small)