General Refactoring

* Added a payment_cancel route
* Renamed manager methods to be more explicit
* Removed unused class properties. Fixed some routes
* Adapting payment services
* Improved PaypalWebCheckoutMethod
* Passed php-cs-fixer and php-formatter
* Small style fixes
* Added URLFactory service
* Improved transaction check and PaypalWebCheckoutMethod
PHPDoc improvements
Fixed array notation php5.3 style
Merge pull request #11 from alch/master

General Refactoring