Allow rulesets to be deleted or allow editing of parameters

[tealeg]

During a cross team meeting with marketplace they pointed out that it was hard to know what parameters you needed up-front. They've ended with lots of duplicate rulesets with version numbers in their names. I can see two way to solve this:

1. (Marketplace's suggestion) - allow us to delete old rulesets.
2. Introduce a concept of rules being "released". Allow parameter editing until a rule is "released".

Discussion required, methinks.