3631 Improve link passthrough in GradebookNG (sakaiproject#3632)

Within the GradebookNG tool, there is a fixed column which appears only
once scrolled to the right. Clicks on elements within that column (i.e.
student name / the row itself) would not be passed through to the actual
element where the event is processed. This fixes that so that the
clicks are passed through correctly, for example: allowing one to
access the student overview panel when scrolled to the right.

This change also removes the scroll left aspect of the clickthrough.

gradebookng/tool/src/webapp/scripts/gradebook-grades.js

@@ -563,9 +563,8 @@ GradebookSpreadsheet.prototype.setupFixedColumns = function() {
   });
 
   // Clicks on the fixed column return you to the real column cell
-  self.$fixedColumns.find("td").on("mousedown", function(event) {
+  self.$fixedColumns.find("td,th").on("mousedown", function(event) {
     event.preventDefault();
-    self.$spreadsheet.scrollLeft(0);
     var cellIndex = $(this).index();
     var rowIndex = $(this).closest("tr").index();
     $targetCell = $($(self.$table.find("> tbody > tr").get(rowIndex)).find("> *").get(cellIndex));
@@ -2583,4 +2582,4 @@ $(function() {
   sakai.gradebookng = {
     spreadsheet: new GradebookSpreadsheet($("#gradebookGrades"))
   };
-});
+});