## What changes were proposed in this pull request?

Shade JPMML classes (`org.jpmml.**`) and related PMML model classes (`org.dmg.pmml.**`). This insulates downstream users from the version of JPMML in Spark, allows us to upgrade more freely, and allows downstream users to use a different version. JPMML minor releases are not generally forwards/backwards compatible.

## How was this patch tested?

Existing tests

Author: Sean Owen <sowen@cloudera.com>

Closes #18584 from srowen/SPARK-15526.