Add examples for `shell` and `command` modules.

I added examples that make use of the `args` form (https://github.com/ansible/ansible-examples/blob/master/language_features/complex_args.yml). This allows people to make their `shell` or `command` actions more clear if they use the options.

I didn't know about this language feature so for me it was quite a search before I found it out. It would be nice to add it to the examples of these modules because you would probably use this language feature faster with these modules than others.