Handle subresource locators with return type Class

This is an extension to the JAX-RS 2.0 standard supported by jersey.
Subresource locators can return a Class<?> in which case the subresource will
be managed by jersey. See section 3.3 of the jersey 2.5 documentation.

https://jersey.java.net/documentation/latest/user-guide.html#d0e2081 (example 3.21)