Add option to force status bar separator to be drawn
Originally when introducing the frameless feature in Breeze, we draw a separator for all the QStatusBar. It turned out that some applications where using QStatusBar outside of QMainWindow::setStatusBar and this broke stuff for them, so we changed to only draw a separator for status bar of main windows which covers almost all the cases.
Dolphin is another exception where a QStatusBar is draw for each split windows and as such is not part of the QMainWindow. In Dolphin we do want to have a separator between the main content and the status bar, so introduce another style hint for this case.
Before:
After: