Print columns as "column C of <relation>" rather than "<relation> column
C".  This seems to read noticeably better in English, as evidenced by the
regression test output changes, and the code change also makes it possible
for translators to adjust the phrase order in other languages.

Also change the output for OCLASS_DEFAULT from "default for %s" to
"default value for %s".  This seems to read better and is also more
consistent with the output of, for instance, getObjectTypeDescription().

Kyotaro Horiguchi, per a complaint from me

Discussion: https://postgr.es/m/20180522.182020.114074746.horiguchi.kyotaro@lab.ntt.co.jp