Add 'direct' keyword to descendants option to query direct children (ep1)

-added 'direct' keyword also to Fetch Descendants Option along with 'all' and 'none' to Query direct child.
-added unit tests to test direct keyword

Issue-ID: CPS-1784
Change-Id: Icb7f59fbeebb03703626132d6d5d2cfde0e5ab4d
Signed-off-by: Rudrangi Anupriya <ra00745022@techmahindra.com>
11 files changed