Enable --mutagenesisType codon & --maxSubstitutions 1

[MaximilianStammnitz]

@andrefaure would it be possible in future to also enable the following option:
--mutagenesisType codon
--maxSubstitutions 1

DimSum (v1.2.11) complains about this:
"Error: Invalid 'maxSubstitutions' argument. Only integers greater than 1 allowed."

... there's surely some applications in which users only want to look at single aa changes (without also providing the full table of expected/permitted variants). :-)

Originally posted by @MaximilianStammnitz in #13 (comment)

[andrefaure]

Very few applications - this is low priority. I recommend just running with default settings and filter for singles yourself from the output (no need to provide a table of designed variants).