Move payload.hpp from public to private headers

:Release Notes:
Removed JSONPayload header from public

:Detailed Notes:
Moved payload.hpp from public header directory into private
JSONPayload used only in unit/integration tests and not exposed to public API

:Testing Performed:
Unit and integration tests on desktop build
:QA Notes:

:Issues Addressed:
[CMB-1066] LS2 C++ unintentionally exposes internal JSONPayload

Open-webOS-DCO-1.0-Signed-off-by: Oleksii Rudenko <oleksii.rudenko@lge.com>

Change-Id: Ib400ca4d5534ed4b1e6dc5e10bb42ae5e38d3061
Reviewed-on: https://g2g.palm.com/6441
Reviewed-by: DCO Verification
Reviewed-by: Oleksii Rudenko <oleksii.rudenko@lge.com>
Tested-by: Oleksii Rudenko <oleksii.rudenko@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Merge branch 'develop'

Open-webOS-DCO-1.0-Signed-off-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Adjust version to 3.9.5

:Release Notes:

:Detailed Notes:

:Testing Performed:
Build and unit tests

:QA Notes:

:Issues Addressed:
[CMB-1066] LS2 C++ unintentionally exposes internal JSONPayload

Open-webOS-DCO-1.0-Signed-off-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>

Change-Id: I4dbad6bb714a7de415a7090347d760f5a4b423f2