Settings: use CMHW serial number

See http://review.cyanogenmod.org/57164

Change-Id: If328ca7b487435b88246d1f8c47b04770183f09e
Merge "Settings: use CMHW serial number" into cm-11.0
Merge pull request #47 from CyanogenMod/cm-11.0

Cm 11.0