[build] Use fixed versions for jxmpp and minidns

[stokito]

The jxmpp and minidns libraries are declared with a version range. You remember #61 where I first time proposed to fixate the version to make IntelliJ happy.

In the Spark I faced another problem that the minidns was resolved into the lowest version. I had to add the dependency manually and also exclude the minidns from smack transitives because the Maven Enforcer "version convergence" rule failed because two versions of the same library in a dependency tree.

We should avoid using ranges. Instead it must be specified the latest know version of library that works fine with the Smack. If an xmpp clients (e.g. Spark, aTalk) needs to use a different version they can define the dependency explicitly.

Also the version range hided the problem that org.minidns:minidns-android21 should be changed to org.minidns:minidns-android23.