Add per-project and per-swimlane task limits

This change allows projects and swimlanes to be configured with task limits that apply to their whole scope (i.e. all active tasks in a project or swimlane, respectively), as opposed to the usual per-column task limits.

app/Template/board/table_swimlane.php

@@ -15,7 +15,11 @@
         <?php endif ?>
 
         <span title="<?= t('Task count') ?>" class="board-column-header-task-count swimlane-task-count-<?= $swimlane['id'] ?>">
-            (<?= $swimlane['nb_tasks'] ?>)
+            <?php if ($swimlane['task_limit']): ?>
+                (<?= $swimlane['nb_tasks'] ?>/<?= $swimlane['task_limit'] ?>)
+            <?php else: ?>
+                (<?= $swimlane['nb_tasks'] ?>)
+            <?php endif ?>
         </span>
     </th>
 </tr>