MCC to ISO country code mapping corrected

ISO code of Democratic Republic of the Congo (MCC 630) changed from CG to CD (CD is correct for Congo - different country, MCC 629)
Added Niue (ISO: NU, MCC 555)
Added South Sudan (ISO: SS, MCC: 659)
Added Tuvalu (ISO: TV, MCC 553)

Change-Id: I3867190d1c34e8e2717eae3e393c0c647c6b2cb0
Reference: ITU E.212: http://www.itu.int/dms_pub/itu-t/opb/sp/T-SP-E.212A-2012-PDF-E.pdf