bad examples in pg_dump README

The ./src/bin/pg_dump README contains several inoperable examples.
First, this suggestion:

| or to list tables:
|
| pg_restore <backup-file> --table | less

seems bogus, i.e. the --table option requires an argument specifing
which table to restore, and does not "list tables". Next, this
suggested command:

| pg_restore <backup-file> -l --oid --rearrange | less

hasn't worked since 7.4 or thereabouts, since we don't have
--rearrange or --oid anymore. (I'm not sure we ever had --oid, maybe
it was supposed to be --oid-order?). Then, three examples claim we
support a "--use" flag, e.g.

| pg_restore backup.bck --use=toc.lis > script.sql

where presumably "--use-list" was meant. Further little gripes with
this README include mixed use of tabs and spaces for the examples, and
lines running over the 80-column limit which at least some of our
other READMEs seem to honor.

I started out attempting to fix up the README, keeping the original
example commands intact, but upon further reflection I think the
examples of dumping, restoring, and selective-restoring in that REAMDE
don't belong there anyway. There are already better examples of such
usage in the pg_dump/pg_restore documentation pages, and IMO that's
where such generally-useful usage information belongs.

I propose slimming down the pg_dump README, keeping intact the
introductory notes and details of the tar format.

Josh