Redesign the CLI.

[mijaros]

With the planned expansion to support other cloud platforms (Rosa, ARO), it is evident that the current way how the cli was designed is flawed and badly maintainable. One of the options is to migrate to click instead of plain argparse. The API of click seems more suitable for the increasing complexity of the necessary interface for osia. This will also enable a more smooth and semantically correct way to introduce new subcommands and ideally register them dynamically per module which conducts such command. Nevertheless, this will mean that the interface of osia will be changed drastically. That's why I think this is a kind of change which is worthy of a new major version, so this issue will be the starting point for the 1.0 release of osia.