Move to webpack

[fcaps]

the current status is we are running grunt for a couple of tasks and webpack for some other. in favor of "well-known" webpack we should move all what's left to webpack.

[] scss -> css [] nodemon -> devserver [] change docker prod/dev [] remove grunt and deps [] remove exceptions from .npmcheckrc

there are surely some issues on the way, but someone has to start it. would be perfect if we also combine it with https://github.com/FAForever/website/issues/500