Correcting required installer package determination to avoid extra packages, thanks to Benjamin Moody <benjamin.moody@gmail.com> (Closes: #739729).

Only automatically do replacements within syslinux configs when they are not directories (as they can be in the pxelinux.cfg case), thanks to Antony Messerli <amesserl@rackspace.com> (Closes: #745760).

This can help facilitate development and testing during the python transition.

Some shells (like dash) will exit fatally when the shift builtin is called
beyond the last option.

* Add function to output unique list of foreign architectures from an
  expanded package list.
* If foreign architectures are detected, add unique architectures
  to dpkg and update apt.
* This requires users to explicitly list at least _one_ package of a
  foreign architecture in their package list (e.g. foo:arch) for any other
  foreign arch dependencies to be handled appropriately.

Silencing copying of syslinux themes since users get always distracted about syslinux 6 files not being dereferenced (which can be totally ignored if you're using syslinux 4).

Pre-emptively removing occurances of the short name of the Debian derivative from Canonical that cannot be named.