The goal was to remove explicit paths where possible.  In the case of
the submodules, this helps to make them more useful as a standalone
repository in case a use isn't interested in cloning the whole mangOH
repository and all of the submodules.

Also updated the developerDay2016 tutorial app to use AVC 2.0 so that
it will work with Legato versions 17.05 and newer.

Remove the commented out gpio initialization code because it doesn't
seem like the gpio interface of the wp85 kernel will change in the
short term and thus the gpio kernel driver isn't useful.

Update comments in Makefile to support Developer Studio

There is an issue where the cp2130 usb to spi adapter chip gets into a
bad state and locks up the USB hub.  Don't enable the module until we
can resolve this issue.

The heartbeat app causes a lot of logging noise on the console port
which makes the console nearly unusable.  For that reason, do not
include the heartbeat app in mangOH Red.

The Makefile is currently broken due to LE-7663.  Disable the Makefile
and update the README to provide build instructions.