Self-optimizing task distribution on threads

[dominicparga]

Every step, tasks of a certain number of vehicles are executed per thread. This number is fix and can be changed by the user. This distribution depends on the number of threads and maybe, it can be optimized automatically. It is also needed in the distribution of nodes. The classes are in the core/simulation package.

[dominicparga]

I've added an interface and a simple implementation of a task-independant approach to distribute tasks to threads. This is still NOT automatically distributed. It uses the same functionality as before (fix number of elements executed per thread in one go), but it is more general than before, because this code is independent of this simulation.

[dominicparga]

Important information: clearing an iterator dynamically (means each thread gets the instance of the iterator and calls next, synchronized) does not guarantee that every element is returned exactly once. Therefore, a static implementation is used (every thread/task gets its own list of elements, which are created and filled by one thread).