sortmerna option for OTU picking added
added fuction build_database_sortmerna
finalized integration of sortmerna in pick_otus
created a failures file from sortmerna output and changed default sortmerna OTU path to QIIME result path
removed debug messages
moved clusters and failures computation to app controller
Merge branch 'master' of https://github.com/biocore/qiime into add-sortmerna

merge changes from master to add-sortmerna branch
added new OTU identifier
updated inline comments
--threads=NUM_THREADS option edited to accept only integer values, as multithreading for usearch, sortmerna and sumaclust creates one thread per core available (default 1)
re-ordered sortmerna_ref_cluster() args
pep8
code review suggestions taken into account
tests added for SortmernaV2OtuPicker class
Merge pull request #1588 from ekopylova/add-sortmerna

Add sortmerna to pick_otus.py
merge conflicts resolved