Replace sortperm by alternative pattern

[bkamins]

Fixes #337

[pdeffebach]

Can you add an example with strings so that its clear ordinalrank is what to do with strings?

[bkamins]

I have added it to the manual (I assume you wanted this).

In general we might think about a more flexible API for @orderby allowing to pass additional parameters (like rev) directly as now it is quite cumbersome. If you want to pass by, lt etc. you essentially need to use sortperm and invperm trick as sortperm accepts all arguments.

[pdeffebach]

@orderby allowing to pass additional parameters (like rev) directly as now it is quite cumbersome. If you want to pass by, lt etc. you essentially need to use sortperm and invperm trick as sortperm accepts all arguments.

Ehhh this doesn't seem so bad. But I'll make an issue to keep track.

Thanks for the PR!