This exposes the option to pass a list of exclude MatchPattern via the
'--exclude' option.
The list is encoded as file '.pxarexclude-cli' in the archives root directory.
If such a file is present in the filesystem, it is skipped and not included in
the archive in order to avoid conflicting information.
Signed-off-by: Christian Ebner <c.ebner@proxmox.com>