Add a single sample extract tool

[znorgaard]

I want to extract UMIs at the speed of rust, but I don't want to make a metadata file. See FastqToBam.

fqtk extract --inputs r1.fq r2.fq --read-structures 5M5S+T +T

Ideally, I want an option to output as an unmapped BAM, but would settle for FASTQ files as V1.