* Adding Java/Scala doc build to Jenkins CI * Deploy built doc to S3 bucket * Build doc only for branches * Build doc first, to get doc faster for branch updates * Have ReadTheDocs download doc tarball from S3 * Update JVM doc links * Put doc build commands in a script * Specify Spark 2.3+ requirement for XGBoost4J-Spark * Build GPU wheel without NCCL, to reduce binary size