Scaling on high dpi displays

[yahbluez]

Issue:
Like many QT programs cq-editor fails to scale useful on high dpi screens.
Often used go around is to set the env variable QT_SCALE_FACTOR to a nice value.

Unfortunately doing that CQ-Editor shows no menu and did not use the scaling.

Only the font in the editor could be scaled by settings.

Solution:
Add a global scale preference or make use of the environment.