implements vectorization and stud logic

[yacine-benahmed]

• Implemented stud logic [Khatib and Fleming, 1998] The stud logic uses the best solution as a parent for all crossover operations -- it is logical for now with placeholder for specifying how many crossovers should occur with the stud.
• vectorized flag for GA on systems where applys are actually vectorized. +fixed a weird bug when calling mutation operation in some circumstances.