Separate webpack config metadata for dev and prod

[tobek]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Build config update

• What is the current behavior? (You can also link to an open issue here)
  Make Webpack Upgradable and DRY #453 has a single metadata config for dev and prod, thereby forcing development environment even on prod builds.
• What is the new behavior (if this is a feature change)?

Prod and dev configs now maintain separate metadata.

[PatrickJS]

thanks!