Rename file fixes

Prevented deleting a file by renaming it to itself.  This is case insensitive for OS X since I believe mac filesystems are case insensitive by default.  Also displayed a confirm dialog when rename would overwrite another file.  Forced the session to reload when overwriting a file so that the overwritten file does not still display.  Also deleted files from the session when they are deleted (when renaming or deleting a file).