Improve CREATE/ALTER PUBLICATION syntax for EXCEPT

Hi,

Attached is a small docs patch to improve the syntax and description of
the EXCEPT clause for CREATE/ALTER PUBLICATION.

The current synopsis for EXCEPT is a bit confusing because both the EXCEPT
clause and except_table_object contain repeated lists:

ALL TABLES [ EXCEPT ( except_table_object [, ... ] ) ]
where except_table_object is:
TABLE table_object [, ... ]

The patch simplifies this by describing the syntax directly:

ALL TABLES [ EXCEPT ( TABLE table_object [, [ TABLE ] table_object ] ... ) ]

and removes the separate except_table_object production. I think
this is simpler and easier to understand. Thought?

The patch also updates the ALTER PUBLICATION description. The current
wording says "adding tables/except tables/schemas", but EXCEPT entries
are not added with ADD; they are replaced or cleared with SET ALL TABLES.
The updated text reflects that and also notes that
ALTER SUBSCRIPTION ... REFRESH PUBLICATION is required for such changes
to take effect on subscribers.

It also includes a few minor wording and markup fixes nearby.

Regards,

--
Fujii Masao