Feature/#8 allow single connections only

[IDragonfire]

approved means I looked over the code^^

@micheljung What is with unit tests?

[micheljung]

@IDragonfire https://github.com/FAForever/java-guidelines/wiki/Contribution-Guidelines#definition-of-done-dod

And please don't approve, since this allows the branch to be merged. Instead just make a "comment" review.

[micheljung]

If you rebase on develop, the build error will be gone and I can merge it

[Geosearchef]

done