Add schema to API.
Add schema to API.

This potentially opens up a bunch of use cases for minimal effort on our part:
  - External metastores (schema not stored in HMS)
  - Schema is in the app. Subsequent stages in chain of MR jobs/spark DAG which
    can use RecordService for intermediate data.

Change-Id: Ibda65ee373c45c06d15887a6888b3399142328f5
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/7309
Tested-by: jenkins
Reviewed-by: Nong Li <99a5e5f8f5911755b88e0b536d46aafa102bed41@cloudera.com>

cloudera/RecordServiceClient,cloudera/RecordServiceClient,cloudera/RecordServiceClient,cloudera/RecordServiceClient,cloudera/RecordServiceClient