HPCC-9842 Add Java Samples to ECL Playground

Fixes HPCC-9842

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #4884 from GordonSmith/HPCC-9842_AddPluginSamples

HPCC-9842 Add Java Samples to ECL Playground

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>