File UI Improvements

Some improvements for file management that are coming out of discussions in the forums:
http://moodle.org/mod/forum/discuss.php?d=169791

-Multiple file upload (like http://moodle.org/mod/data/view.php?d=13&rid=3546&filter=1)-without this feature our schools will not be able to move to Moodle 2.0
-Drag and drop from computer to resource-if a teacher drags a file from their computer onto a Moodle page with editing on it should create a resource
-A course files viewer (a filter that allows a teacher to see all files used as a resource in a course)-this will help courses with multiple teachers see files that other teachers have uploaded
-Upload a file with the same name prompts the user "Overwrite, Rename, or Cancel" to allow users to update and replace an existing file on Moodle.