NeDB Support

**Is your feature request related to a problem? Please describe.**
For smaller projects where a full mongodb server is overkill, it would be great to use `rest-hapi` with NeDB: https://github.com/louischatriot/nedb

**Describe the solution you'd like**
Rather than providing a mongo URI, we could pass in an object that maps model name keys to NeDB datastore instances (i.e., mongo collections).

**Describe alternatives you've considered**
TingoDB, but it appears to be abandoned.

**Additional context**
I haven't looked in detail yet to see if `rest-hapi` uses any parts of the mongo API that NeDB does not support.

If this seems possible, I can help with the code changes.

The issue names no files, tests, or entry points. Start by tracing how rest-hapi accepts the Mongo URI and maps model names to Mongo collections, then compare the API it uses with NeDB's datastore support; done means a documented NeDB configuration works for the supported operations.

Written by the indexing model from the issue text.