Replace matrices.rs with ndarray

[johanneskoester]

ndarray has become the de-facto standard for matrix handling in Rust. I suggest to use that instead of building your own matrix implementation.

[klangner]

Yes I know and agree.
My problem is that I have a lot of problems using this library. Probably that's because I'm learning Rust.
But also I'm not sure about some aspects of its API. To give constructive feedback to ndarray I decided that first I need to learn how to design this kind of library.

So my plan for the first version is to hide matrix module (don't export it). Use my own matrix implementation to learn how the matrix library could be designed in Rust and then provide feedback to ndarray library owner. Add necessary changes (if any) and switch to it.

I will leave this issue open as a task to replace matrix implementation.

[johanneskoester]

Ok, that's fine!