Three PRs for VOResource 1.3

[Markus Demleitner]

Dear Registry folks,

The Exec has recently approved VOResource 1.2 (main new feature:
altIdentifiers on all vr:ResourceName-s) -- thanks to all who
contributed in the various ways.  It ought to turn up on the doc repo
soon.

However, we collected a few open issues on VOResource during the review
ofPR-1.2, and thus I have already started the cycle towards VOResource
1.3.  In consequence, there are now three PRs that I'd invite everyone
here to review:

(1) In mild confusion, we (well: I) added ivo-id attributes to Content
and Creator in VOResource 1.1.  That was a bad idea even back then,
because these interfere with the ivo-id attribute on Content/name and
Creator/name (which have always been ResourceName-s).
<https://github.com/ivoa-std/VOResource/pull/21> deprecates them (in
words; I don't think we have a way to machine-readably deprecate things
in our XSDs).   Thanks to Grégory for spotting this.  I don't think this
is terribly contentious.

(2) The explanations for the various values allowed for Resource/@status
suggested that they were assigned by some sort of registry curator.
That is now how these came out: In practice, it is the publishers
assigning these values (and really, in general they shouldn't use them
in the first place).  <https://github.com/ivoa-std/VOResource/pull/22>
attempts to rectify this and to explain why under normal circumstances,
you shouldn't use anything but active here.  If you ever found you
wanted to set status to inactive of even deleted, please have a look at
this and make up your mind on whether the new language covers what you
need(ed).

(3) While we don't really do any persistence in the Registry, there are
situations in which we want to be able to say "this resource doesn't
exist any more, but there's that other resource that you ought to use
instead".  I'm proposing such a mechanism in
<https://github.com/ivoa-std/VOResource/pull/23>: DiscontinuedResource.

This PR is on top of #21 and #22, so if you review only this, only have
a look at commit 554720c.  And for this, I am not at all positive that
this is what we want to do.  Perhaps just saying "Use whatever record
type you used before but dump all capabilities" would be about as good
(although such a resource certainly shouldn't have any coverage, say).
Anyway, please have a look and totally feel free to blast it if you feel
that's not a good idea.  Perhaps read
<https://github.com/ivoa-std/VOResource/issues/12> before reviewing to
have the context.

As I said: please review when you get a chance, and on (3) think about
whether you have use cases when this would be useful for your resources
(I think I have a few cases, by the way).

Thanks,

         Markus

PS: Btw, if you want to build the document itself, you'll need ivoatex
from its <https://github.com/ivoa-std/ivoatex/pull/157>.  If you find it
in yourself to approve that, I'd also be grateful.