remove prettyphoto from core - this will affect the enhanced photo albums feature on the short term which has been disabled until we figure out how to make the setting per-theme instead of a core option. The library is still available in core (library/prettyphoto) currently but needs to be moved to theme js and loaded/accessed from there [for themes which use it]. Then the library will be removed. It appears that other lightboxes commonly use rel= to group photo albums. So we may provide a generic rel= tag in photo album templates so that the choice of lightbox or album viewer is not only a theme option but could also be accomplished with plugins.