Also use comphelper::Base64 and
DateTime::CreateFromUnixTime to avoid depending on sax.

Change-Id: If1853f8d9481c9caa0625a111707531bbc495f75
Reviewed-on: https://gerrit.libreoffice.org/39993Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Ashod Nakashian <ashnakash@gmail.com>