Make the Entity Resource Reference Resolver pluggable for the Standard URL Scheme

The UC is to be able to contribute a new EntityResourceAction in an Extension, which has a special URL format after the action segment.

For example: /bin/<somenewaction>/some/path/that/represent/something.

Note that it's already possible to register a new ResourceType (ie. what is represented by the first segment in the Standard URL Scheme, e.g. "bin", "webjars", etc).