…nings

- Added `devServerMajor.js` to `razzle-dev-utils` that refactors the detection of the `webpack-dev-server` version in a manner similar to `webpackMajor.js`
- Updated `webpackHotDevClient.js` to use `devServerMajor.js` to pickup the properly cased `createSocketUrl`
  - Hopefully this approach won't break things like the change that was made previously that ended up getting reverted
- Updated `createConfigAsync.js` to use `razzle-dev-utils/devServerMajor` for the `webpack-dev-server` version as well as:
  - Restored `hot: true` to the common `devServer` config and instead only explicitly adding the `HMR` to the plugins for v3 to avoid the following warning:
```
[webpack-dev-server] "hot: true" automatically applies HMR plugin, you don't have to add it manually to your webpack configuration.
```
- Updated `start.js` script to include `devServerMajor.js` so that v4 will `start/stop` the client dev server rather than `listen/close` used for v3
  - Also added `port` into the copied `devServer` config to allow `start()` to work properly

…fore it is used

…tion

…`start()` and `stop()` with a generic error handler