Revise documentation. Add `provide'.

Revise documentation.  Add `provide'.
(pages-directory-for-adding-addresses-narrowing-p):
New user option for adding addresses.  Default to narrowing.
(pages-directory-for-addresses): Intall user settable options.
(add-new-page): Insert new page in specified location.
(original-page-delimiter): Set default value to "^^L".