implement LSCategorySetDescription

:Release Notes:
LSCategorySetDescription now available

:Detailed Notes:
- made lunaservice-meta.h C++ friendly
- factored-out LSHandleGetCategory in category.c
- introduced LSCategoryTable::description field
- added integration test for category manipulations

:Testing Performed:
unit and integration tests on desktop

:QA Notes:

:Issues Addressed:
[BHV-1589] Implement category registration with its description

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

Change-Id: If376cae35e6c063d977f798d505efa322ac69963
Reviewed-on: https://g2g.palm.com/5265
Reviewed-by: DCO Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>