This moves the logic in AbstractXMPPConnection.getSmackTlsContext()
into the ConnectionConfiguration constructor.
Also introduce SslContextFactory and use it in
ConnectionConfiguration.
(yeah, I know)
Sometimes "a friend" has setup an XMPP service which uses a self-signed
cert. While we can get a decent amount of security by using techniques
like e.g. the MemorizingTrustManager, there's still a pitfall. If the
service's TLS certificates contains no or the wrong service/hostname
information, Smack will throw an CertificateException. Therefore provide
an API call to disable hostname verification.
Introducing a clean split between the constant connection configuration
parameters, which are now all in ConnectionConfiguration and the dynamic
connection state (e.g. hostAddresses) which are now in
AbstractXMPPConnection.
Also removed all arguments of login() since the username, password,
resource and callback handler need now to be configured via
ConnectionConfiguration.
Also remove documentation/extensions/messageevents.md, as it's already
in documentation/legacy