Issue #17 : change PacoEvent's experimentName to be plain experiment definition's title
Issue #17 : change instanceId to be the same with experimentId
Issue #17 : remove the design of fetching events to render experiment instances
Issue #17 : improve loading instances from file
Issue #17 : render jsonObjectInstances when saving, so that the newly joined experiments can be stored to file
Issue #17 : remove legacy code
Merge pull request #33 from google/issue17

issue17: disallow user to join an experiment multiple times