Car to manager comm

I've updated a whole lot here. Most importantly: the messaging towards the manager, informing the managing agent of percepts, is now done in the following form:

`elevatorState(Position, Direction, CapacityLeft)` gives the information it states, in the given order. Position is a float giving the exact location, and therefore this update is sent a LOT. The manager should remove the old ones from the mailbox to keep that tidy. Keep in mind this is received as a belief: `received(AgentThatSentIt, elevatorState(Pos, Dir, CapLeft))`

`buttonCall(Level, Direction)` is the **new** form of the message that reports a `fButtonOn(Level, Direction)` percept. I have changed this (old one was 'fButtonOn(Level, Direction)', because it used to look like the percept syntax too much (it was identical). I'd like to evade this because it will make keeping beliefs and percepts apart a lot easier. 

Finally, the `atFloor(Level)` information is still passed on to the manager as it was, and I have left the syntax identical to that of the percept. I've chosen for this because it is not information we will be using, for now, and therefore we shouldn't bother too much about it. This percept is passed on mandatorily, so we have to keep it.

A couple of things that has to be done in the manager file because of these changes, in a listed order:
- [x] Update the way 'it' receives the `buttonCall(Level, Direction)` message, because it now expects `fButtonOn(Level, Direction)`. This should be changed.
- [x] Be able to receive the `elevatorState(Position, Direction, CapacityLeft)` message. (As I'm typing this, `carState(P,D,CL)` might be a better name.. We'll discuss it tomorrow).
- [x] Because the `Position` in `elevatorState(P, D, CL)` is updated so often (8 digit float, *wtf*), the message from the three cars is sent in enormous numbers. We should really tidy up the mailbox as we progress in time, because it'll affect our performance.