Add Ukrainian translation

There is mistake in <code>extension/chrome/skin/inactive-state.css</code> - missing <code>!important</code>.
Also there is no line separating toolbar from page when using [Hide Tab Bar With One Tab](https://addons.mozilla.org/firefox/addon/hide-tab-bar-with-one-tab).

It was too minor for nice Pull Request, so as native speaker I added Ukrainian translation.