base class for entities - provides most common DB ops automatically
entities that don't need auditing
SingletonInstance - temp model for pre-configured singleton instances
playing with "transactions" i.e.
derive from here and list in upgrades above
wiki entries are trashed when deleted - a copy of each older version when udpated or deleted
create a record
delete a record
update a record
represents a mongo db instance
wrap all db operation in this to get logging, timing and stats
main helper for "transactions"