evidence-collection schema for GET /evidence
evidence-collection schema for GET /evidence

currently there is a discrepancy between the schema and returned
json document. the returned json document uses _entities as a root
key due to HAL serialization.

refs #12

OpenBEL/openbel-server,OpenBEL/openbel-server,nbargnesi/openbel-server,OpenBEL/openbel-api,nbargnesi/openbel-server,nbargnesi/openbel-server,OpenBEL/openbel-api,OpenBEL/openbel-server,OpenBEL/openbel-api,OpenBEL/openbel-api