Proper instance and class methods

[nielstron]

Is your feature request related to a problem? Please describe.
Currently classes in OpShin do not support methods. It would be nice to support methods. Especially magic methods (__add__) would improve the situation of i.e. Fractions etc.

Describe the solution you'd like
Users should be able to declare methods on PlutusData classes which will be dispatched to when called from OpShin code.

Describe alternatives you've considered
None

Additional context
Note that this might be more complex than it seems. In particular, the functions should be (C-Style) compiled and mapped somewhere global-statically, then called instead of the attribute accessed (one option). Note also that OpShin does currently not permit inheritance (and does not plan to) which should improve the situation.

Bug bounty: 2000 ADA

[SCMusson]

#389 Is starting on this. Please let me know if this is what you are looking for. Also if there are any particular unit tests you want me to make sure it passes on.