Update Smack to 4.3 branch
Eventually Spark will need to move to the newest Smack branch. As many APIs have changed, this will break a lot of stuff.
Tried to replace 4.1.9 with 4.2.1 in pom.xml. IntelliJ produced lots of errors. But most of them related to JID changes in 4.2. Maybe this is just a simple replace in the code. Don't know.