updated SSA schema for the registry

[Ray Plante]

Hey Doug,

Thanks for the thorough review--particularly in your attention to the 
documentation!  These changes all looks good.  I'm going to propose to 
the group that we adopt this version by Monday and post to 
http://www.ivoa.net/xml.

My only comment is with regard to maxFileSize.  Bytes was chosen as the 
units for consistency with the SIA resource schema.  I think your 
reasoning is good too and am happy to go with this; however, we should 
keep a mental sticky about this when we do SIA v2.0.  We might consider 
revising that schema to use kilobytes as well.

cheers,
Ray