Overriding URL mappings

The Problem

Plugins can provide their own set of URL mappings by including a *UrlMappings.groovy file. This makes it easy for users to get started with such a plugin, but what if a developer wants to use his or her own mappings? At the moment there is no way to hide or remove the plugin-provided mappings, which is Not A Good Thing.

Potential Solutions

• Allow overriding of named mappings (may require namespacing of URL mapping names?) + a "null" mapping that effectively removes a URL, i.e. /some/path -> nothing.