Provide a label DEPRECATED for OEX packages

It would be fair to signal to other users of OEX
that there is no intention to do any maintenance
for a package.
Also, a kind of warning if it is used.

Actually, the only option is to unpublish it.
Just letting it hang around and ignoring Issues and
Pull Request is not acceptable.

In addition, a DEPERCATED package should be free for
adoption and reworking, and eventually fixing
by some other member of the community.