NEWT: Harmonize MouseEvent Pressure (API Change!)

Due to high fluctuation (lack of normalized) pressure values on Android devices,
an option to query the normalized value and access to the current known maximum pressure is required.

MouseEvent:
  - getMaxPressure() returning the [self calibrated] known maximum pressure

  - getPressure(..) -> getPressure(.., boolean normalize) (API Change!)
     - return normalize ? pressure/maxPressure : pressure;