new ebuild: e-gtk-theme

this is a gtk-3 theme matching the enlightenment E17+ default theme.
The ebuild is taken from:
https://github.com/tokiclover/bar-overlay/blob/master/x11-themes/e-gtk-theme/e-gtk-theme-9999.ebuild
Rev: d0f1ceb0687a270739f2d4083d946012f0da7be4