Added centralized theme system and themed all pages

lib/theme.js

@@ -0,0 +1,38 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+(function(){
+	"use strict";
+	
+	let scope;
+	if ((typeof exports) !== "undefined"){
+		scope = exports;
+	}
+	else {
+		scope = require.register("./theme", {});
+	}
+	
+	const settings = require("./settings");
+	
+	scope.init = function(page){
+		const basePath = browser.extension.getURL("themes");
+		settings.onloaded(function(){
+			const links = ["layout", page].filter(function(file){
+				return file;
+			}).map(function(file){
+				var link = document.createElement("link");
+				link.cbFile = file;
+				link.href = `${basePath}/${settings.theme}/${file}.css`;
+				link.rel = "stylesheet";
+				link.type = "text/css";
+				document.head.appendChild(link);
+				return link;
+			});
+			settings.on("theme", function(){
+				links.forEach(function(link){
+					link.href = `${basePath}/${settings.theme}/${link.cbFile}.css`;
+				});
+			});
+		});
+	};
+}());