to CoverArtUtils.

Add <DefaultCover> configuration option to WCoverArt to let skin authors
pick a default cover.

* Move cache key formatting to its own method.
* Explicitly handle the no-size cache key.

Add helper to create a supported cover art extensions regex.

…ils.

* Move cover search out of the CoverArtCache workers.
* Get rid of dedicated table for cover art (and add more columns to
  library table)
* Delete CoverArtDAO and test.
* Add cover scanning to LibraryScanner.
* Load and store cover art in TrackInfoObject via TrackDAO.
* Hook cover columns up to cached TrackInfoObjects in BaseTrackCache.
* Get rid of "ID3TAG" string to identify metadata. Use CoverInfo::Type
  instead.
* Add source tracking for cover provenance (user-selected
  vs. auto-selected) so we know whether it's safe to change a cover
  without losing user data.
* Add helper for reloading cover art from file.
* Use relative paths to cover art so FILE art is not broken by folder moves.

* Communicate selected track instead of cover art.
* Support connecting a WCoverArt to the track currently loaded to a deck.

…eView on requestCover completion for delegate requests.

…and DlgTrackInfo.

* Remove copying of changed cover art into the folder (temporarily?).
* Mark all user-generated change events as USER_SELECTED.
* Remove reliance on CoverInfo::trackId in a couple places.

How did editing metadata work at all before?

Scale (preserving aspect ratio) and cache them by (hash, width)
only. Cropping doesn't really save any paint time since
QPainter::drawPixmap is cheap when you don't have to scale the pixmap.

Listen to the signal in WCoverArt.

* Provide a QObject* requestor pointer when calling requestCover. In
  practice this can be any number you want it to but it is particularly
  useful for the requestor class to pass a pointer to itself so it can
  compare the signal it gets to itself.
* Provide the original CoverInfo request.

require a TrackPointer.

coverart_test

* Update WTrackTableView changes to match new WCoverArtMenu behavior.
* Remove DirectoryDAO integration for now.

Conflicts:
	src/library/coverartcache.cpp
	src/library/coverartcache.h
	src/widget/wcoverartmenu.cpp
	src/widget/wcoverartmenu.h

… library scan.

* Add a request reference integer to CoverArtCache::requestCover.
  Use (pRequestor, requestReference) for de-duping requests instead of
  trackId.

Now only loads a cover once for rows that share the same hash.

Sorts by the hash. It works well except for the case where cover art is
similar but not exactly the same. I think it's good enough to include,
even if some users may be confused why visually similar cover art
doesn't sort together.

Improves scrolling performance when scrolling via keyboard.

interaction timeout.

In DlgCoverArtFullSize, max across all top level windows to get the
appropriate size for the cover art. Maybe this fixes the original issue?

* Adds CoverArtCache::guessCover(s) methods for calling
  CoverArtUtils::guessCoverArt in a background thread.
* Removes processing of reset menu option from WCoverArtMenu and instead
  sends a signal that the owner of the menu should handle.

ControlObjectThread is deprecated all new CO's should be of type
ControlObjectSlave