Port 'Add support for transductive alignment models'

[Enkidu93]

Port any relevant changes in sillsdev/machine.py#327 from machine.py to machine.

[pmachapman]

@ddaspit Did you want me to port ThotSymmetrizedWordAlignmentModel as well? I can't see that this class or its factory have been ported to C# Machine.

[ddaspit]

Yes, I think we will need it to properly support transductive models.

[ddaspit]

I submitted a PR to machine.py that properly cleans up the model when training. I think we can use the same approach for Machine.