sample_type options - handing blanks (negative controls)

[lukenoaa]

Current values are:

• seawater
• sediment
• extraction blank
• distilled water blank
• RTSF blank
• mock community
• positive control
• PCR no-template control
• bead cleanup blank

I would like to change "RTSF blank" to something more generic. Could be "sequencing center blank", or "second PCR no-template control" (more specific).

@ksilnoaa @sammyharding