Rename torch module

[louisfh]

It is confusing, and might be a problem that we have a dependency and module with the same name (torch and /opensoundscape/torch). I propose we change the name of our torch module.

One example of the issue this can cause.
When running import opensoundscape on a machine where you have a copy of the opensoundscape repo you may get ModuleNotFoundError: No module named 'torch._C'

This happens if your working directory is the /opensoundscape directory - as python does not know whether to import our torch module, or the package torch. In one case, even after changing working directory the error persists. I don't understand that.

Here's a comparable issue someone else had
pytorch/pytorch#574