Markup / scss refactor WIP

Fixes #2140
- Mixins file added;
- Markup and -shell CSS from codepen brought over;

src/ui/components/layout/MctStatus.vue

@@ -1,16 +1,9 @@
 <template>
-    <div class="MCT_Status">I'm the status bar</div>
+    <div class="l-shell-head">I'm the status bar</div>
 </template>
 
 <style lang="scss">
-.MCT_Status {
-    position: absolute;
-    left: 0;
-    bottom: 0;
-    right: 0;
-    height: 20px;
-    background: black;
-}
+
 </style>
 
 <script>