base library: provide a parser for command line args

[maxteufel]

Since we now support command line args in both backends (#156), perhaps we want to provide some features to easily parse these. C has getopt(3), Go has the flag package in the standard library, Python has the argparse module in the standard library.

[michaellilltokiwa]

I work on a parser combinator library inspired by rusts nom here: https://github.com/michaellilltokiwa/fuzion/blob/lib/modules/nom/modules/nom/src/nom.fz https://github.com/michaellilltokiwa/fuzion/blob/lib/modules/nom/tests/nom/nom_test.fz

But some bugs in fuzion need to be fixed first for this to work.

[maxteufel]

@michaellilltokiwa I think using general purpose parser for this is overkill. It should be sufficient to work with string.startsWith, string.substring, and string.split.

[michaellilltokiwa]

I disagree, sorry :-D I think the string.startsWith() way is actually more complicated in most but the easiest cases.