signal match 3 orfs upstream and downstream of CvaB

[tijeco]

Sometimes, the best microcin hit doesn't end up too near the CvaB, which may be fine. I think it would also be useful to report hits from the filtered microcin peptides that are three orfs up or downstream from CvaB, as putative exploratory options.

[tijeco]

Proposal: Maybe this doesn't have to be in v1.0.0. I don't think it is absolutely necessary for the initial manuscript, but will certainly be useful in the future when attempting to expand search space.

I propose this gets looped into candidate_immunity, and just change the name to proximal_canditate.