Add ability to remove key/value pairs from JValue

:Release Notes:
Add ability to remove key/value pairs from JValue

:Detailed Notes:

:Testing Performed:
New unit test was written.
Unit tests were successfully run with memory error detection

:QA Notes:

:Issues Addressed:
[GF-3287] Support removing properties on pbnjson objects

Open-webOS-DCO-1.0-Signed-off-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>

Change-Id: I6b2b664c5d9feaebea951d6a4d7476b09b4d592f
Reviewed-on: https://g2g.palm.com/3157
Reviewed-by: Build Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>
Tested-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>