* All desklets: Move icon.png from root to desklet directory
* Some desklets: Remove last-edited flag from metadata
* Some desklets: Remove icon flag in metadata
* Update README & validate-spice script
Inform about new icon location in README
Add some new checks to validate-spice script
* Some desklets: Use symbolic links to icons for multiversion desklets
* All Desklets: Optimize screenshot.pngs with optipng
optipng -nb -nc -o7 UUUID/screenshot.png
* All desklets: Optimize icon.png files with optipng
* hostcheck@schorschii: Move icon.svg into desklet dir
The icon.svg is actually used in Cinnamon
