Added support for CRC-PUF

[b10n]

This adds support for CRC-PUF, which is based on an arbiter PUF and an LFSR with reconfigurable connections. These modifications enable for loading CRPs with multiple response bits and an additional generator polynomial from a file.

[nils-wisiol]

Thanks for adding this, it is much appreciated. The code looks like as if there are some changes unrelated to the CRC-PUF, possibly due to merging/rebasing things. As for the code for CRC-PUF itself, I have not read the paper yet, but it may be possible to fit it into the existing LTFArray.generate_*_transform scheme. Would you mind if I try to re-organize the code to see if I can align it more closely to the existing code style? If yes, my offer would be that I would pull your changes, remove the unrelated changes, reorganize things and then commit with your GitHub handle as coauthor, letting you review changes before I merge. Otherwise, I am open to any suggestions. Thanks again for sharing the code.

[b10n]

The code was written a few months back. While rebasing pypuf/learner/pac/low_degree.py must have slipped through, apologies. And yes, you are most welcome to refactor the code.