Most of the time we just need the descriptions (lib or
opac_description), so let's add a new method for that and cache the
descriptions in L1.
Ideally we should cache it in L2 as well, but the AV code is not robust
enough to allow that
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com> Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl> Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>