use pbnjson in luna-helper

:Release Notes:
luna-helper now uses libpbnjson instead of cjson

:Detailed Notes:
- replace cjson code inside of luna-helper with equivalent in terms of
  libpbnjson API

:Testing Performed:
unit-tests on desktop build

:QA Notes:

:Issues Addressed:
[BHV-6] luna-service2: replace cjson use with pbnjson

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>

Change-Id: I574de4ab4c91ed7ae97e79c8e5ff7500531de174
Reviewed-on: https://g2g.palm.com/4872
Reviewed-by: DCO Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
use pbnjson in luna-send

:Release Notes:
Use libpbnjson instead of cjson in luna-send

:Detailed Notes:
- replace cjson based code with libpbnjson one

:Testing Performed:
unit-tests on desktop build

:QA Notes:

:Issues Addressed:
[BHV-6] luna-service2: replace cjson use with pbnjson

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>

Change-Id: If168c18212c17253bc48ef628f9aceec8b7d57af
Reviewed-on: https://g2g.palm.com/4873
Reviewed-by: DCO Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>