Conditionals feature (#2830)

Introduces conditional styling feature.

src/ui/layout/mct-tree.scss

@@ -1,6 +1,9 @@
 .c-tree-and-search {
     display: flex;
     flex-direction: column;
+    flex: 1 1 auto;
+    //TODO: Do we need this???
+    //padding-right: $interiorMarginSm;
     overflow: auto;
 
     > * + * { margin-top: $interiorMargin; }
@@ -105,32 +108,15 @@
 
         // Object labels in trees
         &__label {
-            // <a> tag that holds type icon and name.
-            // Draggable element.
-            /*border-radius: $controlCr;
-            display: flex;
-            align-items: center;
             flex: 1 1 auto;
-            overflow: hidden;
-            padding: $aPad;
-            white-space: nowrap;*/
         }
 
         &__name {
-           // @include ellipsize();
-           // display: inline;
             color: $colorItemTreeFg;
-          //  width: 100%;
         }
 
         &__type-icon {
-            // Type icon. Must be an HTML entity to allow inclusion of alias indicator.
-           // display: block;
-         //   flex: 0 0 auto;
-          //  font-size: 1.3em;
-          //  margin-right: $interiorMarginSm;
             color: $colorItemTreeIcon;
-          //  width: $treeTypeIconW;
         }
 
         &.is-alias {
@@ -163,3 +149,11 @@
         }
     }
 }
+
+.c-selector {
+    .c-tree-and-search__tree.c-tree {
+        border: 1px solid $colorInteriorBorder;
+        border-radius: $controlCr;
+        padding: $interiorMargin;
+    }
+}