update_kmers_with_alphabet: Update k-mers with alphabet
In piotr-ole/kmer: kmer counting package

Generates and add k-mers (based on the given alphabet) that do not exist in the hash map.

`kmers`	`hash map` reference that stores k-mers (see update_kmers)
`alphabet`	`integer` vector representing encoded alphabet
`currentKmer`	`integer` vector representing the part of currently generated k-mer
`k`	`integer` representing the number of k-mer items
`num2str`	`hash map` representing the sequence encoding between `integer` and `string`
`kmer_decorator`	`function` that can add extra characters for `string` representation of k-mer (for presentation reasons)