Update: use display flex to set equal menu item heights (fixes adaptl…

…earning#466) (adaptlearning#467)

* use display flex to set equal item heights

* inner width keeps the box from collapsing if there's not enough content to push it outward

* remove button container margin for consistent item spacing

less/plugins/adapt-contrib-boxmenu/boxMenuItem.less

@@ -1,5 +1,8 @@
 .boxmenu-item {
+  display: flex;
+
   &__inner {
+    width: 100%;
     margin: 0 @menu-item-padding-hoz @menu-item-padding-ver;
     padding: 1rem;
     background-color: @menu-item;
@@ -38,7 +41,6 @@
   &__button-container {
     display: flex;
     align-items: center;
-    margin-bottom: @menu-item-progress-margin;
   }
 
   &__button {