Allow for different formatting options

[obitech]

It would be nice to allow users outputs other than a pre-formatted table. This would make it easier to pipe the output into other programs such as xargs, etc.

I quite like the way python-openstackclient handles it, where different formatting types (-f table, etc) and different columns can be selected, although that whole feature set might be too big of a change. I'd be happy with just different values, separated by a single space. This way we can use standard linux tools like grep and tr for further processing