Update stats, test corrections icons (#183)

Replace the "i" icon in the header with a bar graph symbol and change
header icon colors (for statistics and test corrections) from green to
black.

Co-authored-by: psvenk <45520974+psvenk@users.noreply.github.com>

public/css/home.css

@@ -380,9 +380,13 @@ i.fa.fa-plus.grades {
   cursor: pointer;
 }
 
+.bar-graph-icon {
+  padding-left: 28%;
+  padding-top: 25%;
+}
+
 i.fa.fa-info-circle,
 i.fa.fa-toolbox {
-  color: var(--green2);
   padding-left: 31%;
   padding-top: 25%;
   font-size: large;

public/js/home.js

@@ -341,7 +341,7 @@ let assignmentsTable = new Tabulator("#assignmentsTable", {
         },
         {
             title: "Stats",
-            titleFormatter: () => '<i class="fa fa-info-circle" aria-hidden="true"></i>',
+            titleFormatter: () => '<img class="bar-graph-icon" src="../images/Bar_Graph.svg" width="28">',
             formatter: cell => (
                 isNaN(cell.getRow().getData().score)
                 || currentTableData.currentTermData