Add a dbf test to the regression suite.
Add the csv-filename-pattern test to the suite.
Fix omitted file dependency (reading queries from file).
Allow any clause ordering in all commands, see #56.

Generalize what the previous patch did only for the MySQL case, this
time affecting the internal parser API expectations to "flag" all
clauses return values with a per-clause keyword so that an ordinary
lambda list keyword can then be destructured.