Housekeeping - Update controller/task code

[JamesGlover]

Describe the Housekeeping

The pipeline controller steps are a little convoluted. We should:

• Avoid running everything via modules included in controllers
• Instead behaviour should be encapsulated in separate step objects. Tasks here are quite nice, but are the configuration persisted in the database for each config step of the pipeline. Instead we probably want to use them to instantiate a separate object, which we then use to process our task.
• Avoid the overloaded task methods, distinct get/post steps, rather than a single overloaded step.

I'm not sure its worth rescuing the existing controllers, but a new system using the same data model at the back end would probably be better.

Blocking issues Describe any other issues or tickets that may be blocking this change.

Additional context Add any other context about the problem here.