upgrade whoosh to 2.5.2
upgraded repoze.profile to 2.0

... no actual changes from 2.0b1 though
some handy logging when stopping bgtasks plugin
cache objects in memory and persist to db in intervals

... and on shutdown. then fill memory cache store upon startup from
persisted database

also treat Keep values special e.g. we only use a maximum age of 30
minutes for them now