refactoring vertex-shader & resource

 - vertex-shader now takes unique_memory, and whether or not the
   stream of data is precompiled or not (HLSL/cso)
 - resource_t got a source-file!
 - get_vertex_declaration fixed up
 - voxels file getting fixed up
vertex/pixel-shader construction

 - now takes data/len
 - create_xxx_shader now takes atma::unique_memory_t
 - now takes a boolean for precompiled file data or not
 - now takes a string for the entrypoint (default: "main")