Change the signature of the read() functions in the readout structures

[lucabaldini]

In the current implementation the three different readout classes have different read() signature---HexagonalReadoutRectangular needs the padding, that the other two do not.

Under the reasonable assumption that the chip is configured once outside the event loop, it would make much more sense for the read() hook to have the same signature for all classes, e.g.

def read(self, timestamp: float, x: np.ndarray, y: np.ndarray)

and add a setup() hook for the configuration part (that is, all the stuff that does not change on an event by event basis.)

If we do somthing along the lines of

def setup(**kwargs)

we might event get away by passing the argparse dictionary to the function. (Let's see how this looks.)