[OpenCOLLADA] Maya2013 workaround for single face geometries

- workaround for maya 2013 crash; -> geometries with single face (one
triangle/polygon)
- fixing trifan/tristrip normal handling if no normal indices available
Merge pull request #174 from GerhardMaier/OpenCollada-Maya2013-workaroundForSingleFaceGeometries

[OpenCOLLADA] Maya2013 workaround for single face geometries