In singletop mode, all frames show the "Quit" option in the file menu
and will quit on Ctrl-Q. When launched from the main KiCad interface,
sub-programs show the "Close" option instead and will close with Ctrl-W.
In this mode, Ctrl-Q will instruct the main program to exit.
Fixes: lp:1779938
* https://bugs.launchpad.net/kicad/+bug/1779938
This was always possible from modal browsers and from the footprint
editor, but it's now also possible from non-modal browsers and the
symbol editor.
Fixes: lp:920380
* https://bugs.launchpad.net/kicad/+bug/920380
Add Display Settings to Footprint Browser.
Make each of them OpenGL on OSX and Cairo on other platforms.
Allow auto-zoom to be turned off and save last zoom setting.
Make ordering of tools in htoolbar consistent.
Standardize grid and zoom drop-downs.
Fixes: lp:1791667
* https://bugs.launchpad.net/kicad/+bug/1791667