1st draft of complete class-based std.random successor

[bearophile]

Joseph Rushton Wakeling:

> Latest patches rename randomSample => sample, again offering a 
> documented alias to assist migration.

Perhaps it's better to not document this alias.


> "permutation" seems good to me (or "permute"?), but perhaps 
> others have suggestions or can point to a typical naming 
> practice from other languages?

I'd like a permutations() range in std.range or 
std.combinatorics.  permutation() sounds a bit too much close, 
despite it is inside another module.

Bye,
bearophile