Modified pick_otus.py and usearch.py to allow modulation of reverse strand matching for usearch.  Also made final sequence assignment to match percent identity of clustering.
Changed comment in code, changed default to False inside of usearch_qf function.
Merge pull request #671 from walterst/pick_otus_usearch_rev

Modified pick_otus.py and usearch.py to allow modulation of reverse stra...