Make a function to make degenerate 5-mer model

[Jason Vander Heiden]

1. Add a function to calculate a 5-mer model from a 1-mer model. Extending the 1-mer to the 5-mer set for one or both of mutability and/or substitution.
2. And the converse.

[Julian Zhou]

added makeDegenerate5merSub/Mut, and makeAverage1merSub/Mut