Add icons at missing sizes, clean up SVG metadata

Adds app icon at 24px, 32px, 64px, 96px. This should give a cleaner look in system menus like App Finder, Whisker Menu.

Removes export path strings from SVGs, metadata which Inkscape added on export.

Note: Inkscape recently changed to save export paths as relative paths so this shouldn't be an issue in the future.