Changes

Remove type bound on IHaveLoader

Allows reusing a single loadable for multiple registries, rather than needing to resort to nesting all the time.
Probably still stuck nesting predicates as that is a generic type to get and and or working

Fix default instances without loaders not serializing properly

Rework how boilerplate loader predicates are registered

Instead of having 3 extra fields in the class, they are all registered automatically in PredicateLoader. In addition, we now have RegistrySetLoader and FallbackLoader to handle other common predicate elements
Static methods were added to the interface to construct the common type as its less clear the loader can handle that
Semantic change: all boilerplate loader types are registered under mantle, this makes the fallback registry work better.

Give generic loader registries names

Will make debug in the console easier, along with JSON errors