Add protein fragmentation

[Koeng101]

This PR is for protein fragmentation. Definitely needs to be cleaned up. Draft for now, but the code is working.

The problem is basically as follows:

• I have a series of proteins that I have mutated using AI / other, derived from a single ancestor. I am going to synthesize these proteins to test them out,
• The protein are rather large, however, and I will be synthesizing them in chunks
• I want for each chunk to be able to be recombined with other chunks from different proteins. Basically, combinatorial assembly!

This PR implements a naive way to do this. Thanks to @ragnorc for the data for testing.

[Koeng101]

I'm going to keep this branch alive for posterity, but also the folks I'm working with have decided it is better for everyone if the overhangs are decided ahead of time. I concur. So this will largely be useless in the future.