add 2D pixmap texture class

remove forgotten noise.h includes common_ply.h: ignore invalid faces with duplicated points (this solves visual flaws in dragon model) extend loadShape for loading triangles realtime_dragon.cc demo: add kd-tree dump/load functionality, add colored perlin cloud texture

material and texture classes moved to material.(cc,h) 2D texture mappings from textures.cc polished and moved to material.h add ColourMap class and subclasses to make textures more flexible two example textures: CheckersTexture and CloudTexture (using Perlin noise)