Add all_perfect_groups

[fingolfin]

We have small groups, primitive groups, transitive groups, but somehow we forgot the perfect groups?

[lgoettgens]

There is https://github.com/oscar-system/Oscar.jl/blob/master/src/Groups/libraries/perfectgroups.jl which I think does exactly what you want, doesn't it?

[fingolfin]

Ah, I was only looking for all_perfect_groups which appears to be missing.

[lgoettgens]

It is unfortunately not as easy to add this, as there is no corresponding GAP function AllPerfectGroups (in contrast to e.g. AllTransitiveGroups) that can be used to bootstrap this.

[fingolfin]

Sure, but it's not that hard either :-). It's not urgent, we can take care of it later this year, after July perhaps