Tax rate was not correctly calculated when added to price
A tax class can now calculate a net/gross price based on its configuration
Use the tax class to calculate price
CS
Converted payment and shipping factory to collection

The payment and shipping collections are a special collection
implementation. They return the model based on the type in the result set.
Payment and shipping methods are now a model
Use models and model relations to access payment and shipping methods
Payment and shipping are real models now, moved into models folder