Adding force to update routine

- Introduced Cache::NEVER Lock (never expiring lock)
- Force flag for dbstructure update
- Moving the business logic to central place in Update class

src/Core/Lock.php

@@ -111,12 +111,13 @@ class Lock
 	 *
 	 * @param string  $key Name of the lock
 	 * @param integer $timeout Seconds until we give up
+	 * @param integer $ttl The Lock lifespan, must be one of the Cache constants
 	 *
 	 * @return boolean Was the lock successful?
 	 */
-	public static function acquire($key, $timeout = 120)
+	public static function acquire($key, $timeout = 120, $ttl = Cache::FIVE_MINUTES)
 	{
-		return self::getDriver()->acquireLock($key, $timeout);
+		return self::getDriver()->acquireLock($key, $timeout, $ttl);
 	}
 
 	/**