This mostly gets ZFS file syncing and file conflict resolution working
with the API sync process. WebDAV will need to be updated separately.
Known issues:
- File sync progress is temporarily gone
- File uploads can result in an unnecessary 412 loop on the next data
sync
- This causes Firefox to crash on one of my computers during tests,
which would be easier to debug if it produced a crash log.
Also:
- Adds httpd.js for use in tests when FakeXMLHttpRequest can't be used
(e.g., saveURI()).
- Adds some additional test data files for attachment tests
