Torch related naming

[brettviren]

Perhaps a minor thing but it's a source of confusion.

WCT has always had a bit of confusion with naming related to torch. There is the pytorch/ subpackage but it uses libtorch and not PyTorch. pytorch.org makes a distinction between these two source packages. Spack has py-torch recipe to install PyTorch. It includes some headers and libraries for libtorch but they do not seem to be complete.

Likeiwse, "libtorch" is used to name wcb --with-libtorch-* options and the LIBTORCH package label.

I propose this renaming:

• torch/ as the sub-package directory
• --with-torch* as the wcb CLI args
• TORCH as the wcb env label
• waft/torch.py as the waf tool
• WireCellTorch/*.h as the includes
• WireCell::Torch as the C++ namespace

I'm interested to learn of any show stopper problems with this proposal in total or in part.

[brettviren]

I expect this sub-package to gain some prominence in the WCT dependency tree driven by SPNG work. This includes providing:

• new IData and INode interface classes which themselves depend on torch::Tensor.
• low-level functions depending on torch::Tensor
• mid-level functions depending on util/ and iface/ as well as torch::Tensor.

It would be nice to resolve this naming issue prior to that new work, even if the resolution is to not change the name.

[brettviren]

Some offline discussion concludes that indeed this is a good thing to cleanup.

I do not want to complicate the next release, which I believe is imminent, and will wait until after it is cut to do the renaming.