The pylorax implementation of the template running code supports
globbing, as well as `--exclude` and `--optional` commands. These
are handled independently for each `installpkg` command, so that
requesting the installation of firmware packages in one command
together with an exclude of `*alsa` does indeed only exclude any
alsa firmware packages but not any other alsa packages. The
previous version of this script would just build an global list
for excludes which has a drastically different result because
a global exclude of "*alsa" would result in a global exclusion of
all matching packages and probably a dependency error.
Therefore, add support for dnf based filtering of packages on a
per `installpkg` command bases, very much like pylorax does.
Add a simple helper that is meant to gather the list of packages
to be installed via a lorax template that uses the "installpkg"
directives. A prominent example is the 'runtime-install.tmpl'
script from lorax-templates-generic, used to create boot isos.
