Slope calibration values are not persisted

[skalarproduktraum]

Slope/galvo calibration values are not persistent between different runs. They therefore have to be re-set again upon startup, otherwise an error message will be shown that they need to be set.

[skalarproduktraum]

This is still the case. The setting should also be moved to the settings tab, as it's usually only necessary to set it once and keep it.