Issue #888: Added PreSale to ItemAvailability.
Issue #888: Added PreSale to ItemAvailability.

vholland/schemaorg,tfrancart/schemaorg,gkellogg/schemaorg,schemaorg/schemaorg,schemaorg/schemaorg,schemaorg/schemaorg,dbs/schemaorg,lanthaler/schemaorg,vholland/schemaorg,schemaorg/schemaorg,unor/schemaorg,gkellogg/schemaorg,tfrancart/schemaorg,twamarc/schemaorg,unor/schemaorg,dbs/schemaorg,tfrancart/schemaorg,lanthaler/schemaorg,dbs/schemaorg,schemaorg/schemaorg,tfrancart/schemaorg,unor/schemaorg,gkellogg/schemaorg,vholland/schemaorg,vholland/schemaorg,twamarc/schemaorg,dbs/schemaorg,gkellogg/schemaorg,twamarc/schemaorg,lanthaler/schemaorg