Check for unused libraries

[tobous]

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As far as I can tell, different Saros components currently contain a number of outdated libraries. Such libraries should be removed from the corresponding projects.

Examples of such libraries are jmdns or xpp3, which are imported into the core but never used as far as I can tell.

To resolve this, we should have a look at which libraries we currently import and which are actually necessary.

[m273d15]

I think xpp3 is used in saros.net.internal.XMPPReceiver (import org.xmlpull.* imports).

[tobous]

But we have two different versions of xpp3. We have xpp3 and xpp3_min. xpp3 is declared in our build file and xpp3_min is included as a transitive dependency. So the declaration of xpp3 might still not be necessary.

[tobous]

Also, it still builds, tests, and runs correctly (at least for Saros/I) if I remove the explicit xpp3 dependency from the core build.gradle file.