Fix JSON schema 'type' keyword parsing

:Release Notes:
Added checking of duplicate values for "type" keyword during JSON Schema
parsing

:Detailed Notes:

:Testing Performed:
Unit tests with memcheck.

:QA Notes:

:Issues Addressed:
[ANG-303] pbnjson: Fix schema keywords validation

Open-webOS-DCO-1.0-Signed-off-by: Mykola Kryvonos <mykola.kryvonos@lge.com>

Change-Id: Ie04b34a4d4bdcf123615a5be33023f3ddd0ce436
Reviewed-on: https://g2g.palm.com/4268
Reviewed-by: DCO Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-on: https://g2g.palm.com/4620
Reviewed-by: Mykola Kryvonos <mykola.kryvonos@lge.com>
Tested-by: Mykola Kryvonos <mykola.kryvonos@lge.com>