various FAQ edits

updates for clarity, to include new Dryad-first workflow, and to
reflect new CLOCKSS situation
added new FAQ to top TOC
removed CLOCKSS bullet
changed CLOCKSS to DataONE
Merge pull request #783 from elizabethdryad/faq-edits

Edits to FAQ and Repository page -- new Dryad-first workflow, no more CLOCKSS -- replaces PR #775