Make the theme name translatable.
Use getters/setters for menu attributes

See: https://github.com/fisharebest/webtrees/commit/231488661263cd50570c97d1f5b4fbf4d11ceca8
Use HTML5 structural markup

See: https://github.com/fisharebest/webtrees/commit/c0f250978363d212adf902e0d3b7006518711fdc