build: Build with colors

Based on tpruvot/chirayudesai's commits, add some color to stdout
and but make it a little easier to customize. Colors are now mapped to
categories and can be edited in Makefile if you or your terminal's
background color do not like them. Defaults:

host stuff: yellow
target stuff: cyan
install/copy: green
filesystem/images: green
imports/exports/includes/notices: green
deletes: red
complete msg: bold green

Coloring can be disabled with "export BUILD_WITH_COLORS=0"

Change-Id: Idcfe9bbf925759f88425f914269855da05c5eef0

Conflicts:
	core/Makefile
Allow a device to generically define its own headers

We have a few cases of devices including specific versions of projects
just because of modified headers (msm_mdp.h comes to mind), and I just
had enough of ifdeffing header files for specific cases (the P990 needs
a lot of these).
Now... if a target defines a TARGET_SPECIFIC_HEADER_PATH, any headers in
there will take precedence over the standard ones; for example, on the
p990, I have

TARGET_SPECIFIC_HEADER_PATH := device/lge/p990/include

which makes, for example, the
device/lge/p990/include/hardware_legacy/AudioHardwareInterface.h be
used instead of
hardware/libhardware_legacy/include/hardware_legacy/AudioHardwareInterface.h
whenever a source file uses <hardware_legacy/AudioHardwareInterface.h>

Change-Id: I41b62668b60e3f62a6ebd3738d8d2675103a81e6