Log Message:
tex-schulmathematik{,-doc}: update to 1.3

* package schulma-physik: load siunitx package with option
  uncertainty-mode=separate; use upright pi in magnetic field
  constant if unicode-math is loaded
* document class schulma-ab: adjust vertical spaces for
  tasks environment
* document class schulma-klausur: adjust vertical spaces for tasks
  environment; new optional argument of the \Aufgabe command for
  the estimated time; writing information concerning the tasks
  to the terminal