Tagging of items

Also-by: Michael Grammling <m.grammling@external.telekom.de>
Also-by: Andre Fuechsel <a.fuechsel@telekom.de>
Signed-off-by: Alex Tugarev <telekom@tugarev.de>
Doesn't this mean that it now does nothing at all, when an item file changes on the filesystem?
Before, it did a full reload - this behaviour should be kept (as long as no "diff" notifications are supported)