Bargraph, and presistance

[thesamprice]

Could you update the bar-graph tutorial to the new plugin api and add it to this tutorial,
and add a persistence plugin to this tutorial.

• bar-graph plugin
• Persistence plugin.

[thesamprice]

Persistence plugin.

I copied the couchdb plugin out into the root directory, and then made two calls to

• openmct.legacyRegistry.register("/persistenceFlask", ...
• openmct.legacyRegistry.enable('/persistenceFlask')

Example can be seen here.
https://github.com/thesamprice/openmct-tutorial/blob/sams/persistenceFlask.js