Milo: Add an option to hide green steps

milo/appengine/frontend/static/buildbot/css/default.css

 /* Copyright 2015 The LUCI Authors. All rights reserved.
  * Use of this source code is governed under the Apache License, Version 2.0
  * that can be found in the LICENSE file.
  */
 
 body.interface {
   margin-left: 30px;
   margin-right: 30px;
   margin-top: 20px;
   margin-bottom: 50px;
@@ skipping 701 matching lines @@
 }
 
 form.command_forcebuild .force-any .force-text {
   display: inline;
 }
 
 div.step-text:first-child {
     display: inline;
 }
 
-.hide .verbosity-Hidden {
+.standard .verbosity-Hidden {
   display: none;
 }
+
+.interesting .verbosity-Hidden {
+  display: none;
+}
+
+.interesting .verbosity-Normal {
+  display: none;
+}