Added Terrain Expansion

[CnC-RaVaGe]

Expanded tile-sets for mappers to create unique and more detailed maps.

Desert map with tunnels, high bridges and water cliffs

Snow Urban map example

• expandspawn13.mix includes Urban theatre tiles.
• expandspawn14.mix includes Temperate theatre tiles.
• expandspawn15.mix includes Snow theatre tiles.
• expandspawn16.mix includes New- Urban theatre tiles.
• expandspawn17.mix includes Lunar theatre tiles.
• expandspawn18.mix includes Desert theatre tiles.

[Belonit]

@CnC-RaVaGe Thank you for your attention and contribution, however, for the reasons stated by @Metadorius, I think we cannot merge this