Add more partitioning schemes for quicksort/quickselect

[piater]

I implemented Lomuto's partition scheme for my own needs, hard-coding the pivot to the last element, because it is the simplest to write down, explain, and analyze. Currently it only lives on my local system in a separate helperLomuto() function.

Let me know if you're interested; if not, just close this feature request :-).

[grant-hollosi]

We would absolutely be interested in that feature! Feel free to open an PR and I'll take a look