The PropertyEnumeration editor (PropertyEnumItem) will check for
separator characeter '|' in enumeration items to auto create
hierarchical groups of items using sub-menus for user to select.
With Sketcher's constraint status label now exposed to stylesheet
control on a per-state basis, add basic styling that is more visible in
this dark stylesheet.
The existing dark themes all have fairly low contrast, which can make
text hard to read. This diff adds a variant of Darker-blue that
increases contrast between text and background.