Decouple Schema Validation

For utility purposes, it'd be quite nice if the Mongoose Schema Validator was a standalone module, and able to validate standalone JSON documents (for example, on the clientside).

Start by locating the Mongoose Schema Validator entry point. Check how it currently handles schema and document data, then define and verify a standalone JSON-document validation path that can run client-side; done means the validator is usable independently of Mongoose.

Written by the indexing model from the issue text.