LP#1330784 Add a sitemap generator for Evergreen

Following the requirements at sitemaps.org, generate a
set of sitemaps that reflect the bib record's last edit
date, with 50,000 records per sitemap file.

Users can run this script targeting different libraries
and generating different output filenames using the
documented options in the script.

Signed-off-by: Dan Scott <dscott@laurentian.ca>
Signed-off-by: Ben Shum <bshum@biblio.org>
LP# 1330784: Release notes for sitemap builder

More like documentation than release notes, but more is probably better
than less.

Signed-off-by: Dan Scott <dscott@laurentian.ca>
Signed-off-by: Ben Shum <bshum@biblio.org>