Add bash completion script

[ali5ter]

It might be useful for the dispatch CLI to generate autocompletion scripts for bash, zsh, etc. similarly to kubectl. In the meantime however, this bash completion script might be useful.

[ali5ter]

@berndtj generated using cli_taxo.py script from https://github.com/ali5ter/cli_taxo. The invocation is:

cli_taxo.py dispatch \ --commands-token '^Available Commands:' \ --commands-filter '^\s\s([\w|-]+?)\s\s+' \ --options-token '^Global Flags:|^Flags:' \ -o bash -O

Here's example of how it could be automated to generate completion file... https://github.com/ali5ter/vmware_scripts/blob/master/vke/create_completion