More type/field updates

- Add `place`, `eventPlace`, and `publisher` to more item types (closes
  zotero/zotero-bits#6)
- Add `publisher` and `place` to `journalArticle`, `newspaperArticle`,
  and `magazineArticle` (closes zotero/zotero-bits#16)
- Add `publisher` and `place` to `webpage` (closes
  zotero/zotero-bits#30)
- Add `place` and `type` for `document` (closes zotero/zotero-bits#18)
- Add `translator` to more item types (closes zotero/zotero-bits#64)
- Add `sessionTitle` (`publication`) and `chair`/`organizer` to
  `presentation` (closes zotero/zotero-bits#60)
- Rename "Rights" to "License" (but keep as `rights` to reduce migration
  trouble) (closes zotero/zotero-bits#63)
- Add many creator types to item types (closes zotero/zotero-bits#77)
- Add `editor` creator type to `report` (closes zotero/zotero-bits#31)
- Move `pages` to `numPages` in `report` (addresses
  zotero/zotero-bits#38)
- Add `number` to `manuscript` (addresses zotero/zotero-bits#19)
- Add `volume` and `issue` to `newspaperArticle` (closes
  zotero/zotero-bits#17)
- Add `isbn`, `issn`, `seriesNumber`, and `series` to `thesis` (closes
  zotero/zotero-bits#15)
- Add `format` to `book` and `bookSection` (closes
  zotero/zotero-bits#14)
- Add `migrations` mechanism (tentative)