impl Ravel._unaligned
impl Ravel._unaligned

Because `Ravel` has a higher priority than `InsertAxis`, it seems unnecessary
to implement `Ravel._unaligned`. However, if the `Ravel` is blocked by some
other array, for instance a `LoopConcatenate`, then inserted axes cannot move
down the function tree and we miss potential simplifications. This patch
implements `Ravel._unaligned` to make this kind of simplifications possible.

wijnandhoitinga/nutils