Show tasks that are due today in a different color

I chose a "Triadic" color from this page,
http://www.colorhexa.com/d90000 it seems to look good under various
categories.

Fix #2285

app/Template/board/task_footer.php

@@ -27,7 +27,11 @@
     <?php endif ?>
 
     <?php if (! empty($task['date_due'])): ?>
-        <span class="task-board-date <?= time() > $task['date_due'] ? 'task-board-date-overdue' : '' ?>">
+        <?php if (date('d') == date('d', $task['date_due'])): ?>
+        <span class="task-board-date task-board-date-today">
+        <?php elseif (time() > $task['date_due']): ?>
+        <span class="task-board-date task-board-date-overdue">
+        <?php endif ?>
             <i class="fa fa-calendar"></i>
             <?= $this->dt->date($task['date_due']) ?>
         </span>

assets/css/src/task.css

@@ -123,6 +123,11 @@ div.task-board-status-closed {
     color: #000;
 }
 
+span.task-board-date-today {
+    color: #0000D9;
+    opacity: 1.0;
+}
+
 span.task-board-date-overdue {
     color: #D90000;
     opacity: 1.0;