Implement more features for the Emacs ``documents provider''

Implement more features for the Emacs ``documents provider''

* java/org/gnu/emacs/EmacsDocumentsProvider.java (queryRoots):
Implement isChild.
(getNotificationUri, notifyChange): New functions.
(queryDocument1): Set rename and remove flags.
(queryDocument, queryChildDocuments): Allow the requester to
detect changes in the directory hierarchy.
(createDocument, deleteDocument, removeDocument): Signal changes
to the directory hierarchy.