Add a bolt task to setup shell completion

[smortex]

This is a building block that might be used when/if we want to add Bolt tasks / plans to setup Choria on nodes not managed by Puppet, in particular client nodes.

Currently our systems administrator manually add the choria repo and install the software, but this is not enough to have shell completion and we might need to update it from time to time.

Add a bolt task that make managing the completions easier:

romain@desktop-fln40kq ~ % bolt task run choria::completion -t localhost --run-as root
Started on localhost...
Finished on localhost:
  Task completed successfully with no result
Successful on 1 target: localhost
Ran on 1 target in 1.31 sec
romain@desktop-fln40kq ~ %