- make landscape deformation operate in a hemispherical fashion - sort of.
- make landscape deformation faster (it deforms the landscape geometry in-place then marks it as dirty rather than rebuilding it all)

Known issues:
- The current hill deformation algo still looks quite wrong on really steep hills.
- it seems like face normals aren't being recalculated, meaning that the lighting is wrong in the indented areas :(

- TODO Try to only deform points that fall within or above the blast radius - eg. not deform points below :/
- TODO Fix lighting after deformation