Provide shell autocompletion

[daniel-j-h]

I was just playing around with the osmium export sub-command to familarize myself with it. Doing so I would have loved shell autocompletion for all osmium commands.

Can we auto-generate and then ship shell completion for osmium's sub-commands?

[joto]

There is code for shell autocompletion in zsh for Osmium in the zsh_completion directory. I believe the Debian packages install this. I am only using zsh, somebody else has to supply this for other shells.