Ahodges/documentation/doc764

@WatsonEmily , please distribute for PM review for usability by our audience.
@jhelbert , @stroilova , @shnayder , @rocha  please review for accuracy, completeness, and level of detail, particularly wrt data czars who will need to revise scripts for post-download processing.
@mhoeber , @srpearce please copy edit.
yes, the syntax for "note", "important" and "warning" indicators is  .. <name>::
Previously, because the dot dot space wasn't present, the note showed up in plain text, just as it appears on the red line above, in the HTML and PDF outputs