Experiment: Test javascript

[sabrina-ulbrich]

This is an experiment to get tests for javascript working. We have to decide if we want that or test only manually. Disadvantages are: tests take longer and need installation of phantom-js, maybe also configuration with travis or docker. So, I think, for such small javascript snippets, we don't need this.

[zaziemo]

@sabrina-ulbrich do you need anything from me here? This PR does not only contain the code to test JS but also other things....

Concerning the tests: I personally like to have JS tests if we'd start to use it more often.

[sabrina-ulbrich]

Only the last commit tests javascript, all others are part of the other PR (not sure, how this happend): database extension. Maybe we should talk on Monday about this.