Add KNS adoption tools for Plasma, global, and cursor themes, color schemes, and wallpapers

This adds a small cli helper tool which allows you to list what Plasma themes are available on the system (and which is the current one), as well as letting you set a theme as the current. It handles being passed a full path to the theme, though when that happens it just uses the last bit of the path as the name of the theme.

The latter part allows it to be used by KNewStuff as an adoption command, and the changes to the knsrc file makes that happen. There is also a small change which fixes a discrepancy in the naming of the Plasma Themes dialog, making it consistent with everywhere else that references Plasma Themes (not sure why they were called styles here, guessing a really old copy/paste thing).

Additionally, a similar tool for the color and cursor KCMs are also added by this patch, and the lookandfeeltool binary built by the global themes kcm is also modified slightly to accept a full path to a package, and added as an adoption command for those.

The patch also adds a tool which sets wallpapers, which replaces the failure-prone dbus command previously used as the kns adoption command.

And just because we all love a screenshot, here's what the --list-themes switch looks like for plasma-applydesktoptheme: