PIR Sensor / Button for Plotclock / -Thermometer

Update #1: Minor bug fix in the Calibration routine -> v1_1b

This are two enhancements for the plot thermometer / clock http://www.thingiverse.com/thing:371248
Such a plot thermometer / clock is a cool stuff but you can't use it for long time as the pen gets empty (or even drys out). This two enhancements makes that it plots only if it is really required:
PIR sensor: if someone is in the room
Button: If you press the button
One or the other can be attached to the plot thermomete