Move header styles into base less

IPython/html/static/base/less/page.less

@@ -37,11 +37,19 @@ div#header {
         height: 0px;
         border-bottom: 1px solid @navbar-default-border;
     }
+
+    @media print {
+        display: none !important;
+    }
 }
 
 #header-spacer {
     width: 100%;
     visibility: hidden;
+    
+    @media print {
+        display: none;
+    }
 }
 
 #ipython_notebook {

IPython/html/static/notebook/less/notebook.less

@@ -90,14 +90,4 @@ p {
 
 .notebook_app #header {
     .box-shadow(@notebook-shadow);
-    @media print {
-        display: none;
-    }
-}
-
-/* Hide the header when printing */
-@media print {
-    #header-spacer {
-        display: none;
-    }
 }