Simplify APIs for tutorial usage

[rbrush]

We found some API improvements that could simplify Bunsen usage when create tutorial content. Specifically, they are:

• Offer the ability to import valuesets from bundles
• Allow valuesets to be broadcast without requiring the ontologies databases to be built if they are not needed
• Offer an API that accepts an RDD of bundles and writes each entity out to disk.

These are are small changes, so I'm wrapping them up into this issue.