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

Reviewed-on: https://gerrit.libreoffice.org/62273
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
(cherry picked from commit 08c3c504)

Conflicts:
	desktop/qa/desktop_lib/test_desktop_lib.cxx
	xmlsecurity/source/xmlsec/nss/securityenvironment_nssimpl.cxx

Change-Id: I7b4df65365893bd5a0628aeec30b3156584849fe