Move webpack config to root

Then we can include all server repo webpack configs in 1 go

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

package.json

     "test": "tests"
   },
   "scripts": {
-    "build": "webpack --progress --hide-modules --config core/webpack.prod.js",
-    "dev": "webpack --progress --watch --config core/webpack.dev.js"
+    "build": "webpack --progress --hide-modules --config webpack.prod.js",
+    "dev": "webpack --progress --watch --config webpack.dev.js"
   },
   "repository": {
     "type": "git",

webpack.common.js

+const core = require('./core/webpack');
+
+module.exports = [].concat(core);