OpenGI version 1.2.0 released

Version 1.2.0 has been released. It defines a new error code, that is thrown when trying to sample a mesh that has not been parameterized onto the unit square. The geometry image rendering now supports point and directional lights and two-sided materials. The problems of the geometry shader based rendering together with vertex texturing or multi-resolution rendering have been completely resolved. A bug, that assigned GI_NO_ERROR the same value as GI_INVALID_ENUM has been fixed, too.