Add an option to include extra info like the URL of a page

It would be useful to have an option to include the URL of the page being captured in the epub and possibly the table of contents for multiple page documents. This could be a toggle per page with a global default. This is very handy tracking where content was obtained and it is useful when doing research where attribution or linking to a source is necessary.

The URL would be included in the page above or below the title.

Additional items that might included are:

- Date when the page was captured
- Name/ID of the person capturing the page (would be a configuration field)
- Browser/save-as-book version used to capture the page