Add empty completion class and test
Add the completion command to the dependency injection container
Add a mock output object to the completion command setup
Add the completion command to the command suite
Inject the completions directory into the completion command
Make the completion command raise an error if no shell is specified
Raise a CompletionNotFound error if an nonexistent completion function is asked for
Get the completions function fully operational
Refactor the completion command into short methods
Handle error message ouput correctly for CompletionNotFound errors
Merge branch 'completion'
Version 1.18.0