fixing watching of files - a path relative to package root is passed to file-watch.tcl but the apm_file_watch proc needs the path to be relative to server root
working around error message reported here: http://openacs.org/forums/message-view?message_id=89854 by checking in ds_user_switching_enabled_p if the nsv exists (this happens at an unfortunate time when the acs-developer-support procs have been sourced, but not the init file)
