Improved cover art assistant
Most Rigelian support questions are related to cover art not displaying correctly. Unfortunately mpd supports cover art retrieval only in recent versions (since 0.21) and the support is still basic. To let the users get the best cover art under these constraints, the cover art assistant in Rigelian is updated with new functions, like selecting which sources are used, the order in which those sources are accessed, and a description how each of these sources work. Also added is the possibility to clear the cover art cache, forcing that all images are reloaded.