QSslSocket: either add method to return the root cert used in a connection or include the root cert in peerCertificateChain()

IIRC peerCertificateChain() only sends the certificates that the server sends, excluding the root certificate. However, when displaying the chain of used certificates, the root certificate should be displayed as well; either there should be a new method or the cert could simply be included into aforementioned method.