Build: update qcom_utils.mk

Add build macro to determine Android Release

Adding platform sdk version 18 for JB MR2.

Change-Id: I79aa831ddd335bd14bd777506c210acc5d9960f1
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.

oldChange-Id: I945b2c38e60b207d2d0f82b34f4f230ac21b0657

Conflicts:
	core/Makefile
	tools/releasetools/ota_from_target_files

PS2: remove assert changes, we don't use it for some reason

oldChange-Id: I945b2c38e60b207d2d0f82b34f4f230ac21b0657

Conflicts:
	core/Makefile
	tools/buildinfo.sh
	tools/releasetools/ota_from_target_files

Change-Id: I2106dfee3d0a4bf20baf87ad85bd9c09c5648888