Input form switcher works

This change adds the input form switcher, which adds a navigation menu
across the top of the input form, letting you switch between different kinds of input.

The input menu doesn't yet look like a nice set of tabs; it could use some love.

js/util.js

@@ -1272,7 +1272,16 @@ var SN = { // StatusNet
             // UI links currently on the page use malleable names.
 
             return false;
-        }
+        },
+
+	switchInputFormTab: function(tag) {
+	    // The one that's current isn't current anymore
+	    $('.input_form_nav_tab.current').removeClass('current');
+	    $('#input_form_nav_'+tag).addClass('current');
+
+	    $('.input_form.current').removeClass('current');
+	    $('#input_form_'+tag).addClass('current');
+	}
     },
 
     Init: {