[tei-council] addition of <availability>

[Syd Bauman]

Kevin and Martin vote for #2.

KH> **I believe I'm on the short list of people who can post to
KH> tei-council even though I'm not a member of this list. Syd, if you
KH> don't see a second copy of this, please forward to the list.**
KH> 
KH> In my comment at
KH> https://sourceforge.net/p/tei/feature-requests/484/#d072 , I actually
KH> argued for:
KH> 
KH> 7. <availability> should be permitted as a grandchild of <monogr>
KH> inside <imprint>.
KH> 
KH> But the recent discussion on tei-council now leads me to support
KH> option (2).