gadgets/generators is a React small application, with a build toolchain

We can ease A LOT the build chain, removing browserify, node and npm requirements, and the Makefile generation of bundle.js (*).

To populate a combobox and run a couple of JS methods, a traditional JS is enough, and so, independently of the fact it was a test project to use React first.

(*) currently not working in the Docker image, as babel/polyfill node fetching process has some issues: it tries to clone through SSH the sources.