Missing functions

[K0bin]

Here are some missing functions I ran across.

MTLHeapDescriptor::set_type

MTLHeapDescriptor::set_resource_options

(the other MTLHeapDescriptor functions too probably)

MTLIndirectCommandBuffer::gpu_resource_id (probably missing for the other MTLResources too)

Thankfully it's fairly easy to work around by just sending the messages manually but it would still be nice if the library was a bit more complete.

[grovesNL]

set_type was added in #316, happy to accept PRs for the others