Like the previous change, avoid exposing the protobuf as a public API
for now. It requires more thought, and is probably better done with
either extra helper accessors like decks.name(), or via a native class.
- expose the data as a writable store
- currently only supports raw HTML; example to come
- fix changes not marking a deck config as modified
- the data is currently packed into the deckconfig object, but we
may move these to a separate store in the collection config in the
future, like is done with decks/notetypes
