Export data easily in JSON, YAML, etc

[ewaters]

One should be able to easily export data to a dump file. Possible syntax:

> select * from faq_questions limit 10;
> .dump ~/faq_questions.json

or

> select * from faq_questions limit 10 | .dump ~/faq_questions.pl format perl

• Context sensitive; will guess output format based on the destination filename extension or by the 'format' argument.
• Can be performed after a statement has already executed and displayed it's output so that you don't need to rerun a potentially lengthy command to get the same data you just saw
• Out of the box support for the following formats:
  • Perl (eval() friendly or Storable)
  • JSON
  • YAML
  • HTML table
  • XML?

[ewaters]

This was mostly implemented in #25. The only thing missing was the ability to dump a buffer that was previously fetched. That's a broader issue, so this issue has been resolved.