Add timestamp sorting to ls-monitor

:Release Notes:
Add -t command line argument for ls-monitor to sort
by timestamps instead of serials.

:Detailed Notes:

:Testing Performed:
Unit-tests

:QA Notes:

:Issues Addressed:
[BHV-5275] ls-monitor output not in timestamp order

Open-webOS-DCO-1.0-Signed-off-by: Alexandr Smoktal <alexandr.smoktal@lge.com>

Change-Id: I79104e007658e0de4fbb0fb231c9f3f06f5470cb
Reviewed-on: https://g2g.palm.com/5468
Reviewed-by: DCO Verification
Reviewed-by: Alexandr Smoktal <alexandr.smoktal@lge.com>
Tested-by: Alexandr Smoktal <alexandr.smoktal@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>