Admin and first setup pages default to dark theme

Since the user facing sides of the UI (login and library) are all dark theme by default, changes the default look for the admin sides (first time setup, admin panel) as well.

dashboard-ui/bower_components/emby-webcomponents/themes/dark/theme.css

@@ -1,8 +1,15 @@
+.skinHeader,
 html {
     color: #ddd;
     color: rgba(255, 255, 255, .8)
 }
 
+.wizardStartForm,
+.ui-corner-all,
+.ui-shadow {
+  background-color: #1f1f1f
+}
+
 .emby-collapsible-button {
     border-color: #383838;
     border-color: rgba(255, 255, 255, .135)
@@ -428,4 +435,4 @@ html {
 
 .timeslotHeaders-desktop::-webkit-scrollbar {
     height: .7em
-}
+}

dashboard-ui/scripts/site.js

@@ -988,7 +988,8 @@ var Dashboard = {
                 }, {
                     name: "Dark",
                     id: "dark",
-                    isDefault: !0
+                    isDefault: !0,
+                    isDefaultServerDashboard: !0
                 }, {
                     name: "Dark (green accent)",
                     id: "dark-green"
@@ -1001,7 +1002,6 @@ var Dashboard = {
                 }, {
                     name: "Light",
                     id: "light",
-                    isDefaultServerDashboard: !0
                 }, {
                     name: "Light (blue accent)",
                     id: "light-blue"