Simulate acceleration

[findus]

Right now train acceleration after stops is not simulated, implement this to get a little more accurate positions.

Basic functionality currently looks like this:
The Logic uses 3 Curves to determine the current location of the train after x seconds (y axis = meters, x axis = time).
The first curves tries to mimic a smooth acceleration, the second one driving with constant speed, and the third one braking before the next stop.

The pink curve indicates the "linear" movement that the app displays right now.

Right now the app implements 2 seperate curves for longer and shorter trips, because with a slower acceleration on short trips the first and third curve overlap with each other, which creates ugly teleporting effects as soon as the function calculates the distance based on the linear curve.

This is still a pretty basic approach, still needs some checking if it is suitable.

[findus]

#17 nearly done