API enhancement: ndarray constructor with strides argument

Short: Please add versions of the functions `zeros` and `empty` that accept a `strides` argument.

Long:
The C++ API of `ndarray` does not allow to create an `ndarray` with the functions `zeros` or `empty` with custom strides. I have a use case in [histogram](https://github.com/HDembinski/histogram) where I need custom strides. This is possible with the underlying C-API, so it is merely an extension of the C++ front-end.

I cannot use `from_data`, because I want the ndarray to own the memory.

Start by locating the C++ ndarray implementations of `zeros` and `empty`, then compare their signatures with the underlying C API that already supports custom strides. The work is done when both C++ functions accept and apply a `strides` argument while the ndarray retains ownership of its memory; add or update tests for the new overloads.

Scritto dal modello di indicizzazione a partire dal testo della issue.