Implement Mongo schema validation

[mikekucera]

Description of new feature

Add schemas when creating the mongo collections.

This should wait until the application is in a state where its almost ready to be released. During active development the mogno document structure may change, requiring the schemas to change. Its better to wait until the document structure has stabalized.

Motivation for new feature

Catches potential errors early, instead of allowing invalid data to be inserted into the DB.
Validates incoming JSON documents to POST endpoints.