bash completion script

[matteocorti]

It would be nice to include in the packaging a bash-completion script.

I wrote a first working version (just the commands and the IDs of installed applications for the uninstall command).

If you want to integrate feel free: https://github.com/matteocorti/mas.completion

[skull-squadron]

The tool itself should output completions for various shells, i.e., mas completions {ba,fi,z}sh

[StefanLobbenmeier]

yeah ideally they are generated by the cli framework, but it seems the PR for adding this to the cli framework was rejected: Carthage/Commandant#120

[rgoldberg]

Closing in favor of #678