QT treats setting minimum size very seriously - it applies even if
the size required by the control is smaller than specified resulting in
rendering too small controls.
- section line convention label
- remove superfluous save/restore on changeEvent
- change default scrub count
- add preference for default symbol dir
- add preference for display of section cut line
as discussed here: https://forum.freecadweb.org/viewtopic.php?f=35&t=53680&p=461356#p461349
* change default tolerance scale to 0.8
* the tolerance scale is directly applied, thus it must have non-italic label
* move tolerance scale to "Dimensions" tab
* move Fuzz settings to "Advanced" tab
* move Conventions to General tab since e.g. the projection angle is an important general setting
* add a note for the label font that this is also used for dimensions and that it there only has an effect for new ones
* use more useful step size of 0.1 for some scaling spinboxes
* sort UI fields in the C++ code to avoid doubled or missing entries (there were 2 doubled entries)
* uniform width of all preferences dialogs
* better alignment for the HLR dialog
