further refactorings

bench/jcobox/bench/tools/BenchRunner.java

bench/results/pgfplot.tex

src/jcobox/internal/Scheduler.java

src/jcobox/internal/Version.java

src/jcobox/internal/stableimpl/AsyncCallImpl.java

src/jcobox/internal/stableimpl/CoBoxImpl.java

src/jcobox/internal/stableimpl/ExecutingScheduler.java

src/jcobox/internal/stableimpl/LinkedScheduler.java

src/jcobox/internal/stableimpl/LinkedScheduler2.java

src/jcobox/internal/stableimpl/QueueScheduler.java

src/jcobox/internal/stableimpl/QueueScheduler2.java

src/jcobox/internal/stableimpl/QueueScheduler3.java

src/jcobox/internal/stableimpl/SimpleSchedulerImpl.java

src/jcobox/internal/stableimpl/SwingScheduler.java