HPCC-12428 Java package support is broken

Java classloader requires . not / to separate packages, but we could not parse
a classname containing a .

Fix both ways - accept / as the package separator, and parse classnames that
contain ., so that either will be accepted.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #6564 from richardkchapman/java-jarfile

HPCC-12428 Java package support is broken

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>