* set environment variables before starting QApp
* fix-422
* Better support of hidpi
* Fix Typo in App-Name
* Remove fontScaleFactor bits
* Add documenation for hidpi displays
- HistogramLUTItem avoids using lookup table if possible
- GradientEditorItem has a method to ask whether the gradient is trivial (can be applied without the use of a lookup table)
- ROI, LinearRegionItem, InfiniteLine no longer redraw for every mouse movement