[AppIcon] redo constructor to take a params object, add "size" param

Add a "size" parameter to allow changing the AppIcon size, and then
simplify the constructor by taking an object with parameters like
gobject-introspection constructors do, rather than taking a large
number of miscellaneous arguments.

https://bugzilla.gnome.org/show_bug.cgi?id=597498

js/ui/altTab.js

@@ -109,7 +109,8 @@ AltTabPopup.prototype = {
         let workspaceIcons = [];
         let otherIcons = [];
         for (let i = 0; i < apps.length; i++) {
-            let appIcon = new AppIcon.AppIcon(apps[i], AppIcon.MenuType.BELOW, false);
+            let appIcon = new AppIcon.AppIcon({ appInfo: apps[i],
+                                                menuType: AppIcon.MenuType.BELOW });
             if (this._hasWindowsOnWorkspace(appIcon, activeWorkspace))
               workspaceIcons.push(appIcon);
             else