Fix normalization of EllipticCurvePoints

[rheitjoh]

(This issue has been imported from the Gitlab repository because it seems to not have been addressed yet)

Original Text (Issue 211)

Currently, there is a method normalize() that returns a new EllipticCurvePoint. I suggest instead to add a normalized version to the existing point or just to replace the point values with normalized ones (which, I think, is never bad).
Furthermore, `normalize() probably shouldn't be public. The user of such points doesn't care. protected should suffice.

Comment by Jan Bobolz

Also: let isNormalized() be protected