TODO:
* switch to the scientific format for axis labels for small numbers similar to what is already done for big numbers (Alexander)
* "default scheme" in the menu for color schemes (Alexander)
* the logic in AxisPrivate::retransformTickLabelStrings() reduces the precision too much in some cases like for the x-region [0,6] with 6 major ticks where we show ticks at 0, 1, 2, 4, 5 and 6 instead of placing the ticks at 0, 1.2, 2.4, 3.6, 4.8 and 6.0.
* use https://api.kde.org/frameworks/kio/html/classKUrlComboBox.html instead of QLineEdit for the file name in ImportFileWidget and save/load the history of used files
* check https://cgit.kde.org/okular.git/commit/?id=7a50ce0edfc9be8bd23441e52a4f3a0c60f7e60f in okular for relevance in LabPlot