Method: Register the gateway settings

Method: Load javascript files and localized variables

Method: Print client ID in header

Method: Capture authentication after returning from Amazon

Method: Set customer details after authentication

Method: Method to check if all the required settings have been filled out, allowing us to not output information without it.

Method: Load additional files

Method: Add filters

Method: Add actions

Method: Show an error message on checkout if Amazon is enabled but not setup.