How to modify the input validation logics for BTE TRAPI API

1. The input validation logics are stored here: https://github.com/biothings/BioThings_Explorer_TRAPI/blob/master/src/middlewares/validate.js
2. It will use JSON-Schema to validate against the SmartAPI stored here: https://github.com/biothings/BioThings_Explorer_TRAPI/blob/master/docs/smartapi.yaml