Add support for queries that don't create tables

[moertel]

Something along the lines of:

When(/^the given SQL files are executed and the result is kept$/) do
  silence_streams(STDERR) do
    @sql_files_to_execute.each do |file|
      sql = File.read(file)
      @result = TESTING_DATABASE.query(sql).map { |e| e }
    end
  end
end