Implement --summary to copy the output to a file, fix #68.

Given than redirecting a tty such as *terminal-io* isn't easy enough,
let's provide a way to copy the summary output to a file. Another way to
solve it would have been to output the summary to the main logs, but
that could have made the logs parsing more difficult that necessary.

Let's see how users like it...
Fix internal API in sqlite, using report-full-summary.