DeviceInfoSettings: Use ro.cm.display.version instead of ro.cm.version

Follows the same logic as ro.build.display.id/ro.build.id:
engineering, debug and unsigned builds will have no distinction,
user and signed builds will show a simplified version

Change-Id: I713ccb2445ea2e333e831129ef7733fd518282eb
Merge pull request #22 from CyanogenMod/cm-11.0

DeviceInfoSettings: Use ro.cm.display.version instead of ro.cm.version