LP#1801759: add mod_remoteip configuration to example Apache config

LP#1801759: add mod_remoteip configuration to example Apache config

Text taken from an OpenSRF patch added by Bill Erickson per bug 1684970.

This patch adds an Apache configuration stanza that uses mod_remoteip
to pass the user agent's IP address to the HTTP translator. It is meant
for when Apache is being run behind a proxy such as NGINX.

To test
-------
[1] Set up Evergreen with Apache and the WebSockets server running
    behind a proxy such as NGINX.
[2] Enable mod_remoteip (e.g., sudo a2enmod remoteip).
[3] Apply the Apache configuration change in this patch, uncommenting
    out the directives and (if necessary) updating the internal IP
    address of the proxy.
[4] Reload Apache.
[5] Perform an action that uses the HTTP translator, e.g., adding a
    vendor record using the Dojo interface.
[6] Verify that the client IP logged is that of the user agent, not
    the proxy.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Bill Erickson <berickxx@gmail.com>