Refactoring build system to support Fuel 6.1

As Fuel 6.1 has changed both Debian package handling (fetching
repositories from Internet) as well as Puppet packaging, the support
for patching these has been disabled.

The pre-deploy logic of Fuel has been removed together with a
number of patches applied on top of a Fuel build, among them
fixes for NTP, DNS and /etc/hosts injection.

Instead, when changed default behavior is required, this will be
introduced as Fuel plugins which more cleanly integrates into the
Fuel system, and also decouples additional functionality from the
ISO build stage.

Signed-off-by: Stefan K. Berg <stefan.k.berg@ericsson.com>