Initial tagged release

feat: major refactoring

- "everything" is now a Resource (with attributes)
- ResourceTypes are now refactored into Profiles, which are Resources
- Validator is core.xillion.cloud aware, and knows how to validate profiles, attributes, data types, etc
- AttributeDefinitions are now Resources
- assets/core.xillion.cloud.yaml for core resources, attributes and profiles
- resource resolver for references
- Resources implement ArrayAccessor
- ResourceContext is mutable