Ability to pass custom config file to wiz command

[mruegenberg]

It would be great to be able to pass a new config file (similar to wiz-config-file in setup.py) to the Wiz command itself.
This would make it easier to test and also not require building Wiz from git when customizing.

My use case is that users only call Wiz through a wrapper script, so I could change the config file in the wrapper script to change behavior for users.