[BB10-internal] QSslConfiguration: add API to persist and resume SSL sessions

Session tickets can be cached on the client side for hours (e.g.
graph.facebook.com: ~ 24 hours, api.twitter.com: 4 hours), because the
server does not need to maintain state.
We need public API for it so an application can cache the session (e.g.
to disk) and resume a session already with the 1st handshake, saving
one network round trip.

Task-number: QTBUG-20668
(backport of commit 3be197881f100d1c3c8f3ce00501d7a32eb51119)

Change-Id: I4c7f3a749edf0012b52deeb495706e550d24c42d
Signed-off-by: Peter Hartmann <phartmann@blackberry.com>