[Frontend] Delivery checkin: final tweaks to CSS

WTD-894
CSS tweaks to allow box-sizing to be applied to elements within mct-include containers;
CSS cleanups

platform/features/layout/res/templates/elements/box.html

@@ -1,3 +1,5 @@
-<div ng-style="{ background: ngModel.fill(), border: '1px ' + ngModel.stroke() + ' solid' }"
-     style="width: 100%; height: 100%;">
+<div
+	class="l-fixed-position-box"
+	ng-style="{ background: ngModel.fill(), border: '1px ' + ngModel.stroke() + ' solid' }"
+	>
 </div>