moltype needs to be fixed in singlesketch

[mr-eyes]

wait! no, moltype needs to be fixed: the moltype that is needed at the beginning of sketching is actually the input moltype, not the sketch moltype -- i.e. is the FASTA file DNA or protein? I think an --input-moltype param might be needed.

@ctb @mr-eyes

Originally posted by @bluegenes in #459 (comment)

[ctb]

also need to check - can you use multiple ksize in a param string? k=21,k=31 etc.