Added cave controls to the ui.
Merge pull request #1 from Skyyrunner/lockbitmap

Changed GetPixel() calls to use a locked bitmap.
Added PointF versions of all the interpolators.
Added settings for light generation and gamemode. No GUI support yet.
Added BesierRivers as a submodule.
Separated the cave generation to a different class. Now I can have more fancy generation without mussing up other stuff.
Got rid of the rather silly operator overloading in the BiomeConversion class.
Brought the cave generation into a single function.
Added two types of caves that vary between each other.