Repeater format

Makes existing Repeater framework more modular to allow for easier additions of new format-standards to format Forms, Cases and other HQ data objects before forwarding. 
This is a bit of a weird way of doing this. How about:
```
if not self.repeater_cls in RegisterGenerator.generators:
    RegisterGenerator.generators[self.repeater_cls] = GeneratorCollection(self.repeater_cls)