Building Site Working Again

- Fixed scrolling of building menu
- Designers add buildings to the Building Menu in the GUI System plus
the icon that is supposed to represent the building into the list.
- Removes building from the list as they are chosen.

Also some other fixes:
- Building parts & textures were either disappearing or turnign black
because to reset the texture, Color.clear was being used. Replaced this
with Color.white, and everything seems to be coming up okay now.