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/swimlane/create.php

@@ -10,5 +10,8 @@
     <?= $this->form->label(t('Description'), 'description') ?>
     <?= $this->form->textEditor('description', $values, $errors, array('tabindex' => 2)) ?>
 
+    <?= $this->form->label(t('Task limit'), 'task_limit') ?>
+    <?= $this->form->number('task_limit', $values, $errors, array('tabindex' => 3)) ?>
+
     <?= $this->modal->submitButtons() ?>
 </form>