Also needed to extend XCertificateCreator with a new method
"addDERCertificateToTheDatabase".

Change-Id: I7b4df65365893bd5a0628aeec30b3156584849fe
Reviewed-on: https://gerrit.libreoffice.org/62273
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>