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/Schema/Mysql.php

@@ -8,7 +8,17 @@ use PDO;
 use Kanboard\Core\Security\Token;
 use Kanboard\Core\Security\Role;
 
-const VERSION = 134;
+const VERSION = 136;
+
+function version_136(PDO $pdo)
+{
+    $pdo->exec('ALTER TABLE `swimlanes` ADD COLUMN `task_limit` INT DEFAULT 0');
+}
+
+function version_135(PDO $pdo)
+{
+    $pdo->exec('ALTER TABLE `projects` ADD COLUMN `task_limit` INT DEFAULT 0');
+}
 
 function version_134(PDO $pdo)
 {