Implement uniqueItems in JSON Schema validation

:Release Notes:
Added uniqueItems property to JSON Schema to check if array doesn't
contain duplicate items. To activate this property, function
has_array_duplicates() should be provided to Schema validation state.
The property is effective during DOM parsing and checking jvalue against
schema.

:Detailed Notes:

:Testing Performed:
Unit test with valgrind

:QA Notes:

:Issues Addressed:
[GF-41896] pbnjson: Implement 'uniqueItems' in JSON schema

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

Change-Id: I3d052028892cb09ca16112089f3fcac3334f764f
Reviewed-on: https://g2g.palm.com/3766
Reviewed-by: Build Verification
Reviewed-by: Mykola Kryvonos <mykola.kryvonos@lge.com>
Tested-by: Mykola Kryvonos <mykola.kryvonos@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>