AGL Distro Policy

Created AGL distro configuration. There is an include file for
common settings used by all AGL distros: agl-distros.inc.
Distro configuration files will include it. There is currently
one distro configuration file for the AGL IVI distro: agl-ivi.conf.

Added an append file for base-files so that we can set the distro
hostname from the distro configuration file.