Remove ConstrainedResourceDefinition, add methods to ResourceDefinition

ConstrainedResourceDefinition is a mechanism to add methods to ResourceDefinition without breaking existing impls. This is not necessary in a major release like WF 8. It exists to make it easier to port RBAC to EAP 6.2, where such potential breakage (in a minor release) is not allowed.

This JIRA is to get rid of this subinterface for WF 8 final.

Deferring this to WF 9 is ok.