Add WebUI mock server and improve hyper-parameter parallel coordinates chart

docs/en_US/Tutorial/SetupNniDeveloperEnvironment.md

@@ -48,7 +48,8 @@ Nothing to do, the code is already linked to package folders.
 #### TypeScript
 
 * If `src/nni_manager` is changed, run `yarn watch` under this folder. It will watch and build code continually. The `nnictl` need to be restarted to reload NNI manager.
-* If `src/webui` or `src/nasui` are changed, run `yarn start` under the corresponding folder. The web UI will refresh automatically if code is changed.
+* If `src/webui` is changed, run `yarn dev`, which will run a mock API server and a webpack dev server simultaneously. Use `EXPERIMENT` environment variable (e.g., `mnist-tfv1-running`) to specify the mock data being used. Built-in mock experiments are listed in `src/webui/mock`. An example of the full command is `EXPERIMENT=mnist-tfv1-running yarn dev`.
+* If `src/nasui` is changed, run `yarn start` under the corresponding folder. The web UI will refresh automatically if code is changed. There is also a mock API server that is useful when developing. It can be launched via `node server.js`.
 
 ### 5. Submit Pull Request
 

src/webui/config/webpackDevServer.config.js

@@ -28,8 +28,7 @@ module.exports = function(proxy, allowedHost) {
     // So we will disable the host check normally, but enable it if you have
     // specified the `proxy` setting. Finally, we let you override it if you
     // really know what you're doing with a special environment variable.
-    disableHostCheck:
-      !proxy || process.env.DANGEROUSLY_DISABLE_HOST_CHECK === 'true',
+    disableHostCheck: true,
     // Enable gzip compression of generated files.
     compress: true,
     // Silence WebpackDevServer's own logs since they're generally not useful.