valid chars need to be in sto for RNAmute. refactor of subopt-neighbors to do the degap so that it is not done in teh subopt-sto part, which makes no sense
refactor of invfold to be more general. removed done-files arg. Added variety of analysis functions to snippets-analysis. Refactor of fold methods in fold-ops to use multimethods instead of cond. Update to read-sto to use similar keys as read-seqs