generate: use transaction handling to give a speed boost
benchmark: various tweaks for thread starting, threadsafe randomness, verbosity etc.
Merge pull request #746 from gimick/generate_speedup

generate: use transaction handling to give a speed boost
Merge pull request #747 from gimick/benchmark_tweaks_1

benchmark: various tweaks for threads, randomness, vebosity etc
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into develop