Extra method on Solver: getBestSolutions().
Maybe rename BestSolutionRecaller to AllBestSolutionsRecaller? I wouldn't keep the first if a couple experiments should little or no performance degradation due to the hashing of each solution step (especially in sim ann).

What do we do with Solver.getBestSolution()?
Proposition 1: remove it
Proposition 2: keep it and return getBestSolutions().get(0)