Actions: Colorize send, clear, update some borders

Changed
- edit-clear (colorized, easier to see in dark themes)
- send-to (colorized, easier to see in dark themes)
          (use purple which already used for other send/share icons)
- user-publicshare (symlink to send-to, public folder icon at <24px will now match send-to)

Updated
- Arrows on most actions made rounded/smoother (same as upstream)
- Borders of many document action icons made semi-transparent, sharper on dark themes
- "Play" icon resized a bit to look more centered, match size of "Stop" icon better

Fixed
- gtk-revert-to-saved-rtl symlinked to document-revert-rtl (was symlinked to ltr)