OptaPlanner benchmark: use in-memory input solution instead of inputSolutionFile

See discussion at http://stackoverflow.com/questions/36779094/optaplanner-benchmark-use-in-memory-input-solution-instead-of-inputsolutionfile

Would like to be able to start a Benchmark run using an unsolved Solution that I have already created with Java code. Use a custom SolutionFileIO class only allows this by using a static variable, or perhaps a ThreadLocal variable (untested).

The answer might be as simple as a setter on PlannerBenchmarkFactory or PlannerBenchmark that takes the pre-constructed Solution as an argument.