Babel-eslint with first refactor

Created by: bolmsten

I have now installed babel-eslint with the rules suggested by Matias. I have also done the first refactoring based on the results from the linting. I managed to remove all errors and now only warnings remain. We can discuss further what rules we should have.

As you will se I have touched almost all files in the repository but it should for the most part be only small changes.