allow comments in json

:Release Notes:
Now pbnjson doesn't report error on comments in json

:Detailed Notes:
- turned on flag allow_comments for yajl
- bumped version to 2.5.0 for proper dependencies from other components

:Testing Performed:
qemux86 build together with luna-service2 that uses pbnjson instead of
cjson

:QA Notes:

:Issues Addressed:
[BHV-2034] We need either support for comments in libpbnjson or role-files stripping

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

Change-Id: I7836653e5bde58357104a5704b47911ddad432fc
Reviewed-on: https://g2g.palm.com/4911
Reviewed-by: DCO Verification
Reviewed-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Tested-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>