Upgrade to Webpack 3

[lukeed]

And remove/replace webpack-blocks in the process?
We currently have to since it only supports 1.x and 2.x

[reznord]

We should, that reduces the bundle size as well (I remember from the previous PR)

Since now that templates are in, we can totally ignore the last PR and create a whole new PR or totally start fresh.

@lukeed would you like to take it? Since you have already sth similar to that