HPCC-9166 Add ECLWatch WU Filters doc

Fix HPCC-9166 Add ECLWatch WU Filters doc
Documenting the Filter options for WUs
in the new ECL Watch interface.

Signed-off-by: g-pan <greg.panagiotatos@lexisnexis.com>
Merge pull request #4328 from g-pan/H9166-FilterOps

HPCC-9166 ECL Watch Filter Ops

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>