Introduces acceleration/deceleration into motion to decrease jerkyness in movements and provide more accuracy in certain situations

This adds acceleration and deceleration to movements so they don't feel jerky and so you can, for instance, accurately jump on top of blocks. What's smooth to one person is floaty to another, but the values can be adjusted. Though, I did spend a fair amount of time fine-tuning these values and I think they should suit most people.