This function calculates an even splitting of a given number of tasks among a given number of workers (threads).
number of tasks to be divided
number of workers
Tasks are labeled consecutively 1,2,...,
nTasks. The tasks are split in contiguous blocks as evenly
A list with one component per worker giving the task indices to be worked on by each worker. If there are more workers than tasks, the tasks for the extra workers are 0-length numeric vectors.