added port recognition to db host

When using a different port than the default one, you can add it like host:port, but the PDO constructor expects another format:

new PDO('mysql:host=xxx;port=xxx;dbname=xxx', 'xxx', 'xxx', array( PDO::ATTR_PERSISTENT => false));

So this litte change now makes it possible to write host:port to the config and it will be reformatted correctly.