Support real-time problem modification during solving with utils for the single thread subsystem

Rete/Drools is single threaded, and so is the current implementation of the localsearchsolver,
but this single thread subsystem should be documented
and utils should be provided to allow for real-time problem modification

A simple way would be to use a producer-consumer pattern with a non blocking queue which holds "problem moves".
Each step the problem moves could be used.

Problems:

• bestsolutionrecalled also needs it's score adjusted. so we'll need a 2th working memory:
  • EITHER temporary, just for the problem move (or set of problem moves)
  • EITHER all the time, but then we'd have to hold a chain of moves, some of which might not be doable at the end
• cached selectors must be notified of refreshing their cache
• solution cloning normally doesn't clone the problem facts, just the proposed solution references. Do we need a full clone now?