HPCC-9391 Refactor DataHandling

Fix HPCC-9391 Refactor DataHandling
doc to faciliate including of sections
in other docs, as needed.

Signed-off-by: g-pan <greg.panagiotatos@lexisnexis.com>
Merge pull request #4441 from g-pan/H9391-DatHan

HPCC-9391 Refactor DataHandling

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>