GitLab

Major Cleanup of SFNO. Retiring non-linear architecture and fixing initialization. Adding scripts for training and validation.

* Updated Changelog

* improved readability of legendre.py

* bugfix in computation of dlegpoly

* Moving conversion from numpy to torch from the legendre module to the sht module

* renaming to vdm in tests.py

* fixing contig in distributed sht

* make it normally contiguous before all to all

* commented the code to be a WAR

* reworked SFNO example

* updated changelog

* Added gradient check to test suite
* reduced size of the unit test
* switched to parametrized for unittests

Without this fix, importing torch_harmonics had run into a module import error
when trying to execute:
```import examples```

Don't import sfno by default (or try/except importing apex)