Add qDebug helpers for CoverArt and CoverInfo.
Early exit in CoverArtCache::requestCover if CoverInfo type is NONE.
Add CoverArtUtils::guessCoverArt helper method.
No need to manually update() DlgTrackInfo.
Improve connection between WCoverArtMenu, WCoverArtLabel, WCoverArt, 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.
Disconnect TIO changed signals while applying track info edits.

How did editing metadata work at all before?
Don't crop cached pixmaps anymore.

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.
Add coverArtUpdated signal to TrackInfoObject.

Listen to the signal in WCoverArt.
Fix test.
Allow segregation of multiple users of CoverArtCache.

* 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.
Move cover art to the Deere track text row.
Make a CoverArtUtils::selectCoverArtForTrack variant that doesn't
require a TrackPointer.
Load the player's loaded track into WCoverArt upon creation.
Use QStylePainter in WCoverArt so we can style the widget with CSS.