lazyset: add order awareness to the class Just a bit of extra code makes the lazyset aware of order. This renders orderedlazyset useless. At some point, the `subset` will become responsible for this ordering logic. But we are not there yet because the various objects used as subsets are not good enough.

lazyset: remove min/max This is now handled by abstractsmartset.

baseset: remove min/max methods This is now handled by the base class.