Update database after tags are edited

For some reason nobody updated the database when tags where edited.
Problems:
- When editing many songs the Tagedit dialog stays open longer (which I think is ok).
- If there are calls to TagReaderClient::SaveFile (non blocking) which expect to return really fast we might not return as fast. There are some places where this is called and I could only test Inline Editing which is fine with this change.
- I didn't test CDRip.

P.S.: Initially I tried to use NewClosure to call the new function but I couldn't make it work. If somebody wants to take a stab at it, be my guest.