Private files needs to look like more of a core functionality

Currently the private files block is the only way to manage the private files. But the private file area is not part of the block and should not be dependent on whether it's available or not.

We need to fix this so that:

1) There is a main interface in /user/files.php and /user/filesedit.php and /user/filesedit_form.php
2) "Nav -> My profile -> Private files" goes to /user/files.php
3) The block displays the file tree as it does now, but the edit button goes to /user/filesedit.php and then it comes back.