Add support for stuff like [target [target2 [target3] ...]]

I do not know the correct term for the feature, but something like: "anonymous options" that is
always listed at the end of the commandline.

Currently one access these options via
cmdline.getArgList(), but e.g. the
HelpFormatter does not include these in its usage print
and they are not verified by the parser. e.g. man command line is required to have at least one page
argument, but that is not checkked by the parser - that should be possible.