Can you add Combination and Permuation function?

[Trần lê duy]

Reference

https://en.wikipedia.org/wiki/Combination

https://en.wikipedia.org/wiki/Permutation

[Axel Kramer]

For combinations there's a SubSets() function.

And the Binomial() function.

Examples for Permutations

Permutations({a,b,c,d})

Permutations({a,b,c,d},{3})

ToDo: have to add these functions to overview page: Combinatorial

[Axel Kramer]

Fix #157

→ <<cset 774e7962b366>>