Add more operations

[Jonatan Kłosko]

Not all operations are practical to implement them on tensors, but I'm positive we can add these:

• random selection (with and without replacement, configured via an option)
• clip (reducing all genomes to a specific range, useful for real representation)
• shuffle (shuffling rows in the population matrix, useful when using natural_selection to randomize parent pairs)
• two point crossover
• n-point crossover (ideally without point collisions; this is pretty much a generalized two point crossover, but I think we can implement two point crossover more efficiently) (#27)