DAE Exporter

Added possibility to export Collada files (.dae) to BabylonJS file format (.babylon).
The exporter uses the same logic as the FBX exporter. The file is loaded thanks to a XNA loader in memory and XNA classes are used to export to BabylonJS file format.
Since this logic could be used for other 3D formats files, I renamed FBXExporter to XNAExporter and made it abstract. Concrete subclasses of it are the specific exporters: FBXExporter and DAEExporter. In the concrete subclasses you just have to override XNAExporter::SupportedExtensions, XNAExporter::Importer and you can override XNAExporter::ExtraPipelineAssemblies.

As Collada importer to XNA I chose ColladaXna and added it as submodule. For now it points to my fork of Bunkerbewohner/ColladaXna since I fixed a bug in it (I also discovered that it doesn't deal with up_axis and distance unit so I may add some code to fix that) but of course it should later point directly to Bunkerbewohner/ColladaXna.

Since it could be helpful, I added a Visual Studio 2010 solution to contain projects related to export. I had to change the framework version though.

I commented the part telling Visual Studio to copy generateAll.bat to the bin folder since the file is not in the repo.

I also applied fix provided in #106