Properly identify SQL statements of form UPDATE....SELECT as non-query.

Current implementation of isQuery() does not identify SQL of the form:

    UPDATE foo 
    set <whatever,whatever,whatever>
    where foo.<somefield> in (SELECT <somefield> from bar....)

as a non-query, requiring both a r/w connection and not returning a record count.

Pull req. adds a precedence check for SQL r/w verbs to flag these properly, along with some unit tests in the "test-plugin" profile.