Allow discussions to be hidden and restored

framework/core/less/forum/DiscussionListItem.less

@@ -3,6 +3,12 @@
     max-width: none;
   }
 }
+.DiscussionListItem--hidden {
+  .DiscussionListItem-content {
+    opacity: 0.5;
+  }
+}
+
 .DiscussionListItem a {
   text-decoration: none;
 }

framework/core/less/lib/Badge.less

@@ -33,3 +33,7 @@
     display: inline-block;
   }
 }
+
+.Badge--hidden {
+  background: #888;
+}

framework/core/less/lib/Dropdown.less

@@ -50,8 +50,8 @@
       }
 
       &.disabled {
-        opacity: 0.5;
-        background: none;
+        opacity: 0.4;
+        background: none !important;
       }
     }
     > a, > button {