🎨 Add theme support

- Move root (var) style properties to `/assets/css/themes.scss`
- Improve mobile navigation
- Create section component for the collapsable sections.
- Create logo component, so color can be changed.

- Add settings page
- Add option to select theme color
- Add option to select theme background
- Add option to enable/disable multi-colored frames.

- Add settings to VueX Store
- Persist VueX store in LocalStorage.

plugins/vuex-persist.js

@@ -0,0 +1,5 @@
+import VuexPersistence from "vuex-persist";
+
+export default ({ store }) => {
+    new VuexPersistence().plugin(store);
+}