* Mark feedItems read in a single batch SQL update
* Automatically remove old feed items
* User-facing preference globally and per-feed for feed item expiration
- Hide notes, tags and related for feed items in itembox
- Add feed support for <enclosure> elements
- Add feed syncing methods for synced settings (additional work is
needed on the sync architecture to download synced settings from the
server)
- Change feed item clear policy to be less aggressive
- Adjust for deasyncification
- Disable translate-on-select
- Closeadomasven/zotero#7, Remove context menu items from feeds