Return summary of mutation positions

[Taepper]

Add function that receives list of mutations and returns every subset of these mutations with the count, how often this subset occurs together

summary([2A,3C,5C,89C])
=
{[2A],count:5}
{[2A,5C],count:123}
{[2A,89C,5C],count:50}
{[2A,3C],count:2}