Make ajax file list URL work in IE8

For browsers that don't support the history API,
the URL query will be stored in a hash
Automatically convert files URL to hash URLs for IE8 and less

Since IE8 and less don't support the history API, we need to use
hashchange as a workaround. To make this seamless the server will
initially convert the URL to a hash URL in such cases.
File list is now always ajax loaded

The file list is not returned any more by index.php in the "files" and
"files_trashbin" apps. The list will be empty and loaded initially
by the client using an ajax call.
Files app now work with both URL hash and URL query

The files app now reads the current directory from both the URL hash and
the URL query. This makes it possible to exchange links to directories
between IE8 and non-IE8 users.