Update the JS tooling

* get rid of gulp
* use webpack-dev-server to serve app.js
* express serves static files
* 2 webpack configs: local and production
* for development with backend, websocket URL is injected
* remove unneeded static files

client/Dockerfile

@@ -1,6 +1,5 @@
 FROM node:0.10
 WORKDIR /home/weave
-RUN npm install -g gulp
 COPY package.json /home/weave/
 RUN npm install
-COPY gulpfile.js webpack.config.js .eslintrc /home/weave/
+COPY webpack.local.config.js webpack.production.config.js server.js .eslintrc /home/weave/