Allow the use of the same wheel more than once

[ffraenz]

The current implementation skips wheel combinations featuring the same wheel more than once (e.g. I, I, III). For attacks of historic messages, this makes a lot of sense. However, for messages that originate from today's (online) Enigma simulators, this is no longer a limitation. A flag should be added to disable skipping such locations in the key space.

Current workaround: Define a custom wheel with the same wiring and turnover but a unique name and reference it from the slot wheels. Wheels of different names are not considered equal.