Added basic structure

Added the basic structure for the Clickpleteness project. Also set up a linter, a build chain and a unit test framework. This MR is to prepare everything to the point that the next MRs are more or less mainly Clickpleteness content.

• The linter is ESlint using the quite strict prettier rulesets.
• Building the app is based on node.js, that means source files (css, js, ...) are separated from distributed files.
• The build command "compiles" (bundles together) all files from the src/ folder into respective files in the app folder.
• Unit testing is done with Jasmine. Test scripts are in the spec/ folder.
• The testing is done on a headless (no UI) chrome/chromium browser. That should make it possible to test every aspect of the app before deployment.

I set up a, for now, three stage CI to cover the before mentioned points: linting, building, testing

All the required tools are also mentioned and linked to in the README.

\approve @marius, @ds, @fd, @nicgar \fyi