Support for webpack-dev-server in development mode

[bsharrow]

The s2i run script only supports nodemon for hot deployments when DEV_MODE=true. To use webpack-dev-server, I can set DEV_MODE=false and then override NPM_RUN but that results in my build and deploy env using different values for DEV_MODE and NODE_ENV.

Perhaps the run script can be updated with a new environment variable so hot deployments can be started with a different package than nodemon.