envsetup: Mark zsh as compatible

Basic functionality has been tested on zsh 5.0.2 and has been found to
work correctly.

Change-Id: I02e5e3bedf56b43104c280d9737ae7b334357643

Conflicts:

	envsetup.sh
core/Makefile: update BOARD_CUSTOM_BOOTIMG_MK fix
this updates code left out from commit fd88ca3

Change-Id: I86ceb22001b92f1b631000d0cefa84a64d11370e
core: main: remove all the spam about including make files

Change-Id: Ifd2ef0e239d16b169c572472416c2c31df62a367
envsetup: do not print an error if complete fails

complete is a bashism; so it will fail on other shells. Avoid printing
an error if that is the case.

Change-Id: Id6d6311792f409cc3a697c7a2bb003863f1afe60
build:  Add USE_SET_METADATA tag

On some of the older devices the recovery doesn't support
metadata when setting permissions.  This allows to use
set_perm vs set_metadata you will need to set
USE_SET_METADATA := false inside your boardconfig.mk

Change-Id: Ib6cf97b5ca28cee8a87975231f3a61b156e77d29