add $GENOME_LENGTH param

[kapsakcj]

So we can allow Flye, filtlong, and others to adjust params based on user-supplied genome length

[kapsakcj]

Will need to think carefully about this, especially in regards to having organisms on the same sequencing run with differing genome lengths.

Might require that the user supplies a samples.tsv or something to match samples, barcode numbers, and estimated genome length