Heightmap editing in editor

[cyanskies]

• [x] New tile selector UI
• [ ] New interfaces
  • [ ] set starting height in "new map" and "resize" etc.
  • [x] setting height diff and direction(higher/lower)
  • [ ] smoothing terrain
  • [x] set terrain to specific height
  • [ ] Adding bumpiness to terrain
  • [ ] creating ramps
  • [x] create cliffs
• [x] add default tile height to terrain settings
• [x] add an alternate grid drawing system that plays nice with heightmap terrain