Update Root container images to Spark 3
Upgrades to the Root container images:
- Include Spark 3 (utilize built-in Hadoop, since it now supports S3/MinIO without modification)
- Use combined images rather than download and install Hadoop/Spark separately
- Include Sonador client libraries
- Drop BeakerX and incorporate Spylon-Kernel instead
- Include Octave and R in the image
Edited by Rob Oakes