Missing __ne__ magic methods

[tomato42]

While on python 3, __ne__ is implicitly defined to mean not (x == y), on python 2 that is not the case.
See this excellent answer on stack overflow for details.
As such, we need to make sure that for every __eq__ we have a __ne__.

Missing ones:

• ecdsa.ellipticcurve.PointJacobi
• ecdsa.ellipticcurve.Point
• ecdsa.ecdsa.Public_key
• ecdsa.ecdsa.Private_key
• ecdsa.keys.VerifyingKey
• ecdsa.keys.SigningKey
• also check that we don't use assertFalse(... == ...) or assertTrue(... == ...) in test coverage after fixing this