Pybinding for sdk

[freeranged3v]

Ready for merge.
Please note the formatting changes for vm.rs, these are from cargo fmt, no semantic changes.

[parazyd]

@freeranged3v I implemented some pythonic functions for Base and Scalar. Can you do the similar things also for Point?

It should support __add__, __mul__, __sub__, __neg__.

Perhaps also worth adding functionality for += and -= in Base, Scalar, and Point.

[freeranged3v]

Perhaps also worth adding functionality for += and -= in Base, Scalar, and Point.

FYI, Python automatically implements += with __add__ for example.

[parazyd]

Thank you!