AdminCustomerController override

Override of AdminCustomerController.php to show username in customer
create form and customer list, in back office.
Added function searchByName to Customer override

Overrided function searchByName so on creating new order from back
office customer can be searched by username. Also removed comments as
they stay after module is uninstalled.
Merge pull request #8 from razaro/master

AdminCustomerController override and modification of Customer override