Authority resource class

[Ray Plante]

Hi Tony,

I've been playing with the Authority resource class with our modified 
structure, and I'm wondering if we need to register AuthorityIDs as 
separate resources.

A possible alternative is to have the AuthorityIDs listed as metadata of 
the Organization that owns them.  
  Advantages:  
   +  simpler: when multiple authIDs folded into the Organization 
      description, there's less information to provide when registering a 
      new authID.
   +  use of xsi:nil="true" is not needed (otherwise, the Authority 
      description must use the xsi:nil in the its Identifer/ResourceKey). 
      It allows us to be hard-nosed about requiring a ResourceKey with an 
      identifier in all cases (by removing nillable="true").  

  Disadvantages:
   -  Must update the Organization description with each new authID 
      "registered".  ??

thoughts?

cheers,
Ray