Paypal unreliable getting payment processor type
Newer versions of CiviCRM will set the "payment_processor_type_id" parameter, but older versions may set payment_processor_type instead.
- Add a helper function to get the PayPal processor type (Paypal Standard, PayPal Pro, PayPal Express).
- Use that helper function in PayPal classes to find out which processor type we are.
This fixes PHP e-notices and ensures that the correct PayPal type is selected each time.