Add bash completion for CLI

[spalladino]

We would like to have bash autocompletion for the CLI.

As a first approach, we could add autocompletion for the commands themselves (see this issue on Commander for a discussion on how to integrate commander with autocompletion), so when a user types zos, the available commands are autocompleted.

A more complete approach would be to then add autocompletion for the arguments, such as autocompleting with the contract names available when running add. This may require to add more informational output to zos so it can provide this information to the autocompletion script.