[WFLY-1069] Support reads of the model with expressions resolved

Supercedes Joe's excellent work at #69.

This adds a new commit disabling resolution of vault expressions. The article at https://developer.jboss.org/wiki/JBossPasswords-NotSecureButRecommended provides an excellent overview of theory behind the vault. The key thing is that the entire vault concept requires the vault user to have both the vault expression, which is readily available, and physical access to the vault. Allowing an API open to remote clients to read the vault defeats the main point. We don't allow the existing :resolve-expressions op to resolve vault expressions for this reason. So I don't want to create an exception to this policy for this work.

So I added a commit that changes the resolution to one that cannot access the vault, but which won't fail in the presence of unresolvable values, simply returning the value unresolved.