Guess bit_cutoffs in hmmsearch

Hi Martin,

I'm trying to align multiple HMM to proteins; some of my HMM has a GA score, and others do not.

Is there a way to leave hmmsearch to guess if he must use the bit_cutoffs for this HMM? It would be great to have this possibility rather than make two batches of HMM. I would also leave the possibility of forcing the bit_cutoff as an option.
I know it's a little to do two batches, but the inside code of the pipeline is a little more complex, and as Pyhmmer reads the HMM to get the cutoff values, if the cutoff line begins with GA, we could save the `gathering` type of cutoff.

Let me know if you think it's a good idea and if you could add this or not in the future.

Thanks