Added the ability to rename existing pages.
[[!redirects Some Page Name]] redirects Wikilinks [[Some Page Name]] to
the current page (assuming "Some Page Name" does not exist).
Real pages trump redirects (though this may change, depending on
user feedback).
From Jason Blevins:
Create a "History" page for each wiki page.
Link to it, and to the "Diff" page from "Recently Revised".
Also, correct a bug in listing/deleting links to uploaded
video and audio files.
For the file_list action, include the pages which link to the given file(s).
This required rejiggering so that that information is actually retained in the database.
Unfortunately, you'll actually need to revise the page(s) in question, because that's the
only time this information is updated in the database.
