tasks for bam2fq pipeline

[hexylena]

Checklist

• Pull request details were added to CHANGELOG.md.
• Documentation was updated (if required).
• parameter_meta was added/updated (if required).
• Submodule branches are on develop or a tagged commit.

here i've

• Added biopet task for validating fastq (it's a nice tool! Thanks for writing it.)
• Updated the samtools.Fastq task based on discussion in chat, I need to be able to specify the singleton location in addition to 1/2