HPCC-9933 Bundle tool does not properly support multi-file bundles

Confusion between a directory containing a single file (for simple bundles
distributed as a ZIP) versus directories that contain an ecl file per exported
symbol.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #4788 from richardkchapman/ecl-bundle-dir

HPCC-9933 Bundle tool does not properly support multi-file bundles

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>