Ensemble mode

[agroce]

Implement deepstate-ensemble that runs multiple fuzzer jobs, at least AFL/libFuzzer/Eclipser, and cross-seeds without user fuss. Should work with just number of cores as an argument, and automatically allocate cores nicely, use a good generic cross-seeding strategy. https://arxiv.org/pdf/1807.00182.pdf has some research on the utility, and ideas to mine.