Simplest possible sort impl

This ist the simplest possible sort implementation I found (the one in libc++ is too optimized). 
It allows to at least try the sort interface.

Test using default comparison are provided.

TODO:
- test using iterators, custom comparisons, and projections.
- test file needs cleaning.
> We still need a better way to create a range [0, 10) than ranges::view::take(ranges::view::iota(0), 10);

I know.

> Same issue with for_each (can't do for_each(ints(0,10), ... ) due to rvalue range.

Repeatedly pointing out that it's not ideal doesn't make the problems go away.

> The proposal needs to relax range-based for since it expects iterators with the same type.

Yes. I think that's the only language change we need. Shouldn't be too hard. The change is trivial.