This commit adds
- SmackReactor / NIO
- a framework for finite state machine connections
- support for Java 8
- pretty printed XML debug output
It also
- reworks the integration test framework
- raises the minimum Android API level to 19
- introduces XmppNioTcpConnection
Furthermore fixes SMACK-801 (at least partly). Java 8 language
features are available, but not all runtime library methods. For that
we would need to raise the Android API level to 24 or higher.
This commit adds the modules smack-omemo and smack-omemo-signal.
smack-omemo is licensed under the Apache license like the rest of the smack project.
smack-omemo-signal on the other hand is licensed under the GPLv3.
Due to the fact, that smack-omemo is not of much use without smack-omemo-signal,
the OMEMO feature can currently only be used by GPLv3 compatible software.
This may change in the future, when a more permissively licensed module becomes available.
Fixes SMACK-743.
