Add support for duplicate validation to list attributes
[WFCORE-443] When an overridable directory is defined in the system properties and the directory grouping is set to by-server (the default) ensure the server name is appended to the directory.
Merge pull request #404 from jamezp/WFCORE-443

[WFCORE-443] When an overridable directory is defined in the system prop...
Merge pull request #390 from ctomc/validators

Add support for duplicate validation to list attributes
[WFCORE-484] Remove no longer needed cast to AbstractResourceRegistration