replace ocamlbuild by dune + update code + autoformat code

[grazil]

Hello, I update the project because I could compile it.

I decide to use dune as it is recommand on the ocamlbuild website to make the change.

I modify the source code to make it work with the last version of js_of_ocaml.

I use ocamlformat to unify the code formatting.

Hope you will accept my merge request.

Thanks for this wonderfull project and have a nice day !