Load/Store Data from/to Database

[penghou620]

stuartf:
We use helenus as a client to cassandra for data persistance. In Hilary we then write a dao.js to abstract that into an api, you can see an example at

https://github.com/sakaiproject/Hilary/blob/master/node_modules/oae-content/lib/internal/dao.content.js