Color clouds which only have xyz data

Some .ASC files do not have color or normal data. In those cases we need to color the point cloud somehow. We can either do this by making the cloud a 'color cube' or we can generate the normals ourselves and light it.

Our best bet is to probably auto-generate the normals, but we should put this off until later. Maybe we can get the users to use a 3D authoring tool to add normals until we implement our own algorithm.