Added Setters and getters to the physics file

I had added setters and getters for the Motion class in my physics file.
I am still not sure how I want to set up my move function... as I found
that storing the Object wrapped inside of the Motion class, causes the
object to be copied into the motion object. So, if someone wants to
modify the object outside of the motion class, the changes will not be
made to the copy inside of the class. I am trying to find a nice way to
get things to work so they can reference the same memory address.