(#2677) - local docs start at 0-1, don't save _revisions

Two things:
* local docs should start at 0-1, not 0-0. This is not strictly
  necessary to solve the bug, but I find it easier to understand
  when we do exactly the same thing as CouchDB.
* CouchDB tries to "help" us by also giving us a revision object
  (e.g. `"_revisions":{"start":0,"ids":["5"]}` for rev `'0-5'`),
  which we save ver batim and then return back when you do a GET
  on that same local doc. That confuses CouchDB and it ends up
  giving us the wrong _rev the next time it PUTs the doc.