Allow devices to specify certain ro. props via TARGET_UNIFIED_DEVICE

This modifies buildinfo.sh to not set model, name, description, and
fingerprint in build.prop. These can then be set via custom init
lib.
This also fixes ota_from_target_files to function without these
props being preset.

Change-Id: I945b2c38e60b207d2d0f82b34f4f230ac21b0657
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_build into kk44
Merge remote-tracking branch 'aosp/kitkat-mr1.1-release' into HEAD

Change-Id: Ice2071e60ec88b49d6f6640bbd6c20bc2af8bda4
Merge pull request #2 from scotthartbti/kk44

MAJ