Add management API descriptions for alias resources and attributes

When a resource or an attribute is an alias for a different resource or attribute, the management API description data should include information describing that relationship.

For an attribute, an alias relationship is different from an 'alternatives' relationship, as the latter is a mutually exclusive arrangement (one alternative must be undefined if the other isn't) while with an alias, both attributes will exist but will always have the same value, and attempting to set them to different values (e.g. using both as params with different values in an 'add' op) is invalid.