Improve hotend PID

[ErwinRieger]

Look into http://brettbeauregard.com/blog/2011/04/improving-the-beginners-pid-introduction/ and see if pid algorithm can be improved. Maybe http://brettbeauregard.com/blog/2011/04/improving-the-beginners-pid-introduction/, http://brettbeauregard.com/blog/2017/06/proportional-on-measurement-the-code/ can be used to avoid temperature overshots. Maybe faster material profile measurement possible.