Support line commenting with '#'

[matentzn]

Low priority, should be dealt with in bulk when doing another major push on dosdp tools. I have seen (for example in ENVO) that people try to comment out rows in a template for provenance reasons.

[dosumis]

This should already be supported in templates. Templates are just YAML and # is the standard line comment character. That was one reason for choosing YAML of JSON for the standard. (Or does this refer to TSVs? Support there would be harder).

[matentzn]

It's for the TSVs! Debugging a series of cases where people tried to commend out rows in the data TSV files..