Added inactive state to window title bar

- When a window is neither key nor main the title bar is clearly different
- capp_lint ThemeDescriptors.j
- Renamed some layers in Aristo2 PSD to be more descriptive
- New artwork files for window close buttons
- Removed stray Aristo2 image
Merge branch 'refs/heads/inactive-window'

Conflicts:
	AppKit/Themes/Aristo/ThemeDescriptors.j
	AppKit/Themes/Aristo2/ThemeDescriptors.j