Add command line arguments module

[aleksisch]

Now whenever we're adding a new tool we rewrite command line arguments parsing.

Das has strong macros and they should be utilized. We can inspire by rust approach, something like:

require daslib/clargs

[Args]
struct Config {
    name: string 
    opt: int
}

[export]
def main() {
    let cfg = Config.parse()
}

After that all (most?) calls to get_command_line_arguments‎ should be rewritten using this macro.