Update ndarray dependency to v0.16

[alex-appetiti]

Hey @jonasBoss , thank you for your work on the repo.

I've gone ahead and updated the ndarray dependency to 0.16.

This involved the following extra changes:

• When including ndarray in the dev-dependencies in Cargo.toml the feature flag for approx is now just named approx rather than approx-0_5.
• .into_shape(...) is now deprecated, so I've replaced all instances with .into_shape_with_order(...)

[jonasBoss]

Thank you for the update! I will try and get a release ready in the upcoming weeks.