Separate assemblies for separate samples

[avani-bhojwani]

Description of feature

Transferring Slack request to Github:
Currently the pipeline pools reads from all files in the samplesheet before proceeding with assembly. However, some users would find it useful to keep different samples separated and be able to generate multiple transcriptomes with only one run of the pipeline.
"I would absolutely love the pipeline to be upgraded to treat sample sheet entries with different sample names as different entries that should be kept separately, just as other nf-core pipelines such as Sarek and Rnaseq does."

[davidecarlson]

Just wanted to second this request. I'm running the pipeline for the first time, and the idea that the pipeline would combine all samples did not even occur to me as a possibility!