Add support for other scalar types from the `num` crate, such as `Rational32` and `Rational64`.

[PanieriLorenzo]

There is already support for Complex32 and Complex64 from num, consider adding support for other numeric types from that crate.

Related to #1229

[Nil Goyette]

This issue, with the current title and description, is #1229. Please clarify what you need, here or in #1229, or close this issue.