Move "opta" to separate theme package.

themes/opta/Makefile.am

themes/opta/README

themes/opta/bottom-active.xpm

themes/opta/bottom-inactive.xpm

themes/opta/bottom-left-active.xpm

themes/opta/bottom-left-inactive.xpm

themes/opta/bottom-right-active.xpm

themes/opta/bottom-right-inactive.xpm

themes/opta/close-active.xpm

themes/opta/close-inactive.xpm

themes/opta/close-pressed.xpm

themes/opta/hide-active.xpm

themes/opta/hide-inactive.xpm

themes/opta/hide-pressed.xpm

themes/opta/left-active.xpm

themes/opta/left-inactive.xpm

themes/opta/maximize-active.xpm

themes/opta/maximize-inactive.xpm

themes/opta/maximize-pressed.xpm

themes/opta/maximize-toggled-active.xpm