kcms/{colors, cursortheme, desktoptheme, icons}: improve deletion of themes
Reason for the change
The kcms that feature delete buttons were somewhat inconsistent regarding 1. whether they would allow you to delete the theme and 2. what tooltip to display.
- Some kcms would not grey out the delete buttons of system-installed themes. It is probably better to have them greyed out, since the user can't delete them. Also, some kcms didn't allow deleting the currently selected theme, while others did. I think it makes sense to not allow deleting the active theme (you wouldn't be using it if you really wanted to delete it), so I made this consistent across these kcms.
- Most kcms just show "Remove Theme", even for greyed out buttons. I changed this so that it aligns with how lookandfeel does it, i.e. "Remove theme" for enabled buttons, "Cannot delete the active theme" for active themes and "Cannot delete system-installed themes" for system-installed themes.
Issues
- Unsure whether the tooltips are good. Particularly how to capitalise them (Previously, this was somewhat inconsistent, some were title-case, some were lower-case...). Suggestions are welcome.
- For some reason, desktoptheme does not recognise breeze as system-installed and thus I am unable to grey it out for the breeze themes (other system-installed themes were classified correctly).