support translation during sketching?

[bluegenes]

As of v0.3.2 we only allow DNA --> DNA sketches, protein --> protein, dayhoff, hp.

We could enable translated sketches, but then we would need a way to either specify both the input moltype and output moltype, OR specify that a sketch is translated. If the latter, we could make a new sketch param in core that describes whether it is translated.

• ref store is_translated metadata in minhash sourmash#2219