Update Chat plugin to use Smack 4.0.0

The 'use-tls' property was wrongly named, because SASL != TLS. So it got
replaced with an 'accept-all-certificates' property, which, when
enabled, will make Smack accept all presented certificates.

Smack 4 throws more exceptions, as it is no longer hiding the
concurrency involved when dealing with network connections. Therefore it
was necessary to change a few catch blocks to catch Exception.

I've backported TLSUtils from Smack 4.1-SNAPSHOT. Re-licensing it (GPLv3
vs. Apache License 2.0) should be no problem, since I'm the copyright
holder for the Smack version too and willing to provide it under the
GPLv3 in Freedomotic.

Once Freedomotic switches to Smack 4.1, then TLSUtils should be remove
from the Freedomotic codebase in favor to the one provided in Smack 4.1.
Chat Plugin: Add 'manual-hostname' setting for XMPP

Why burden the user with configuring a hostname and a port? Instead let
the magic of DNS SRV do the work for us as default. If the user really
wants to configure the XMPP server's hostname and port, the still can do
it by setting 'manual-hostname' to true.
Small adaption on pull-request #27
first draft of mqtt-client plugin
changed client mode as asyncronous