Move CoverArtCache::extractEmbeddedCover to a utility class.
Minor test cleanups.
Prevent deep-copy of QImage while checksumming it and move calculateHash
to CoverArtUtils.
Move CoverArtCache::cropImage to CoverArtUtils.
Move CoverArtCache::rescaleBigImage to CoverArtUtils.
Some NULL-safety changes.
Remove 'widget' from method / var names.
Move CoverArtCache::searchInTrackDirectory to CoverArtUtils.
Misc. fixes.
Remove default cover handling from CoverArtCache.

Add <DefaultCover> configuration option to WCoverArt to let skin authors
pick a default cover.
More misc.
Avoid doing file I/O in the main thread.
Move CoverInfo to coverart.h. Add CoverArt struct.
Refactor to use the common structures in coverart.h.
Cache-key improvements.

* Move cache key formatting to its own method.
* Explicitly handle the no-size cache key.
Hash the full-sized image, not the cropped or size-capped image.
Only check QPixmapCache if we have a non-empty cover hash.
Add a debugging flag to CoverArtCache.
Pull file extension regex generator into a utility file.

Add helper to create a supported cover art extensions regex.
Add source and type fields to CoverInfo and equality operators.