Argument Labeled

Add a handful of convenient methods to Module, which make working with argument hashes in Ruby a bit easier.

Requirements

This only works with Ruby 1.9. This, however, is as far as I know no big problem because there is also a gem for Ruby 1.8.

You shouldn't redefine any of the *_arguments methods (as in
```
class Test; def self.default_arguments; nil; end; end
```
because then you won't be able to use the ones from our package unless you use ::Module.default_arguments
default arguments are to be passed as blocks returning hashes.