Use more standard icons

Use more standard icons

- Replace ui_tabcomp.png with go-last named icon,
  fixing gdk_pixbuf_new_from_inline deprecate warning
- Replace gq-icon-rotate-counter-clockwise.png with object-rotate-left named icon
- Replace gq-icon-rotate-clockwise.png with object-rotate-right named icon
- Replace gq-icon-filp.png with object-flip-vertical named icon
- Replace gq-icon-mirror.png with object-flip-horizontal named icon
- Replace gq-icon-info.png with document-properties named icon
- Use recommended pan-{down,up}-symbolic named icons