Initial Bootstrap 3 migration

src/UI/Content/Bootstrap/utilities.less

@@ -3,28 +3,54 @@
 // --------------------------------------------------
 
 
-// Quick floats
+// Floats
+// -------------------------
+
+.clearfix {
+  .clearfix();
+}
+.center-block {
+  .center-block();
+}
 .pull-right {
-  float: right;
+  float: right !important;
 }
 .pull-left {
-  float: left;
+  float: left !important;
 }
 
+
 // Toggling content
+// -------------------------
+
+// Note: Deprecated .hide in favor of .hidden or .sr-only (as appropriate) in v3.0.1
 .hide {
-  display: none;
+  display: none !important;
 }
 .show {
-  display: block;
+  display: block !important;
 }
-
-// Visibility
 .invisible {
   visibility: hidden;
 }
+.text-hide {
+  .text-hide();
+}
+
+
+// Hide from screenreaders and browsers
+//
+// Credit: HTML5 Boilerplate
+
+.hidden {
+  display: none !important;
+  visibility: hidden !important;
+}
+
 
 // For Affix plugin
+// -------------------------
+
 .affix {
   position: fixed;
 }