Makefile: Fix target display

Change-Id: I07e60e6b9a6b09d798ca50c6295072828b643a50
envsetup: Add pushboot function

This function lets you push a file from your current OUT dir
for your current device. It root/remount the device, push the
file, and reboots it. Example: pushboot system/app/SystemUI.apk

Change-Id: I8a404323a4091e8502fbdd24198c66f1ac598192
envsetup: Set CUSTOM_BUILD environment variable

This is used to gate a few features, including backuptool

Change-Id: I02fee9e0765cca88c833bb0514762aa3b14642e3
Add backuptool support to the releasetools system

Pulled from CyanogenMod 10.1

Change-Id: Iffd9a45865011ad9108508d31f79e53d609dd6f4
build: add support for custom releasetools

Change-Id: I2337559ac669bb5868708c4726cbacbf5713261a

Conflicts:
	core/Makefile
Enable backuptool by default