Restructure and tidy up of code

Code has been tidied and restructured, in addition typing has been introduced for functions

Ringstellung Feature Added

Ringstellung is the name given to the extra layer of encryption whereby the internal wiring of each rotor could also be rotated.

Message Five Character Grouping

Output now groups letters into sets of 5 characters matching a typical enigma read out

Robust Key Checks

Implemented by @nasfarley88, key checking is now more robust to prevent invalid keys being used.