Fix aria warnings

[mburri]

Check the console output for warnings concerning missing aria labels

[gobeli]

Most of the components are tested in isolation, without going through jsonforms and no labels are set because of this. That's why during the tests the aria-warnings show up. How should we go about this? suppress the warnings?

[mburri]

I think we should focus on the example application - not the test output.

[mburri]

on a closer look - all warnings in the browser console are caused by the SpectrumTableArrayControl - we should probably implement #90