ArrayRef instead of ArrayBase in function interfaces

Hi,

I frequently find myself wanting a read-only array in Python backed by a Rust-owned buffer (usually to print it in an interactive session).
For this I use PyArray::borrow_from_array which takes a &ArrayBase as parameter.
I would like this function to take a &ArrayRef instead to be able to use it with a greater variety of arguments.

While this is a breaking change, I reckon the necessary code changes at call sites would be small, since ArrayBase already implements Deref<Target=ArrayRef>.

In my quick search I only found a couple of places, where this proposed change could be applied

• PyArray::borrow_from_array,
• PyArray::from_array,
• impl ToPyArray for ArrayRef (? not sure about this one).

Another consequence would be to bump the minimum version of the ndarray dependency to 0.17.1.

Kind regards!

Start with the implementations and documentation for PyArray::borrow_from_array and PyArray::from_array, then inspect the impl ToPyArray for ArrayRef and the ndarray dependency declaration. Check all affected call sites and existing project checks; done means the proposed interfaces and dependency requirement are updated consistently and the project still builds.