Catch "MySQL server has gone away" with MySQLi too and exit properly
Allow If-Unmodified-Since-Version to be 0
Remove quotes in error message to match test
Update shard.sql to match live schema
Settings sync, via classic sync and API [schema change]

Restricted to the 'tagColors' setting for the moment
Drop pre-3.0 sync clients, and update some version-related error messages
Change column name [schema change]
Additional collection-item tests
Support passing dateAdded/dateModified in item JSON
Remove unused 'libraryEnabled' field [schema change]
Fix for PHP 5.4 bug
Return 404 instead of 500 on invalid item key
Merge zotero branch 'upstream/master'