Added possibility to process PayPal Express orders

[norgeindian]

This commit adds the possibility to also process PayPal Express orders, as these do not throw the event checkout_submit_all_after.

[milansimek]

@norgeindian FYI: There's a bug in the code:

require_once Mage::getModuleDir('controllers', 'Mage_PayPal') . DS . 'ExpressController.php';

Should be:

require_once Mage::getModuleDir('controllers', 'Mage_Paypal') . DS . 'ExpressController.php';

(Mage_Paypal instead of Mage_PayPal)

[norgeindian]

@milansimek , thanks for the hint. Changed the pull request accordingly.