Construction heuristics need to scale even with a high valuerange size: support selectedCountLimit

If the construction heuristics need to return in seconds or less, and the value range count is high (10 000 values or far more) and the entity count is also relatively high, than it might not return in time.
The solution is to support selectionCountLimit (and use it together with random selection), so the CH trades a little bit of solution quality for a lot of speed (and Local Search can use that extra time to make up far more than that solution quality).

Already works on master.
Basically I want to backport these 2 commits:
https://github.com/droolsjbpm/optaplanner/commit/965c5d6d5005df6052c3630e12d4077b2464c56a
https://github.com/droolsjbpm/optaplanner/commit/6a9d72b6d