LP#1301955: disable autosuggest by default

Until we solve the accessibility issues caused by autosuggest as noted in
https://bugs.launchpad.net/evergreen/+bug/1187993, we shall disable the
feature by default for new installations.

An entry for the release notes is included.

Signed-off-by: Ben Shum <bshum@biblio.org>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>