Meshbuilder

added methods to build with Meshes and added a test project for MeshBuilder
The backing array is modified as it transforms the vertices (which you would always do when inserting a mesh because not transforming them would just keep placing the mesh in the same place), then it's bulk copied into the mesh you're building. I suppose I could just insert the transformed vertex directly into the mesh instead of using a backing array. I'm not sure now why I was so in love with a backing array.