default name for the catalog

[Lauren Wood <lauren@softquad.com>]

The discussion we had last time reminded me of an issue which isn't in
the issues list.

In part B of 9401, there is a system of default names of the catalog,
which gives the implementation a way to bootstrap itself when finding
the catalog. 

I know some of you think of this as a packaging issue, which I don't; I
simply want a way for an implementation to look for a file by default
which it can treat as a catalog. If there is a package, this file could
either be in it, with the default name, or not.

Lauren