Registrar Modules

Registrar modules are largely the same as regular modules except for 3 things:

1. They should be set to registrar instead of generic for the module type in the config.json file (Module Configuration)
2. They should extend the RegistrarModule class, e.g. class Mymodule extends RegistrarModule
3. They should implement the necessary methods from the RegistrarModule class (Module Methods#registrar-methods)