Empty fields in CSV

[yashpatel6]

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Adding option to allow empty fields when parsing a CSV. Tested with metapipeline-DNA PR adding CSV support

[nwiltsie]

As-is the parser isn't robust to quoted strings containing commas, but that is orthogonal to this change. Overall this looks good.

[yashpatel6]

Agreed, the current parser is fairly bare-bones and won't really handle cases with commas and such in quoted values