Meshbuilder

added methods to build with Meshes and added a test project for MeshBuilder
I'm not sure about this method name, if might be confusing (e.g. `MeshBuilder#mesh(Mesh)` could as well specify/set the mesh you're are going to build). Perhaps something like `MeshBuilder.add(Mesh)` or `MeshBuilder.addMesh(Mesh)`. I'm not great at naming though.