Creation of Sleepable interface + some minor fixes

src/example/philosophes/MainPhilosophe.java

src/example/randomants/Ant.java

src/example/randomants/MainAnt.java

src/mas/core/Cyclable.java

src/mas/core/Schedulable.java

src/mas/core/Sleepable.java

src/mas/core/ThreeStepCyclable.java

src/mas/core/TwoStepCyclable.java

src/mas/environment/TwoDCContinuousGrid.java

src/mas/implementation/schedulers/AsyncCycling.java

src/mas/implementation/schedulers/FairCycling.java

src/mas/implementation/schedulers/FairPosCycling.java

...implementation/schedulers/PausableThreadPoolExecutor.java