Allow to hide source maps in prod mode (and still show them in dev mode)

[smessmer]

I want source maps to be available in dev, but not in prod.
If this is not the default behavior you want, you could introduce this as a config option.

Many play apps are using different application.conf for dev and prod. If the availability of source maps could be configured using a key in application.conf, people could easily switch off source maps in prod environment.

I don't mind about the performance of building source maps in prod. I'm fine with always building source maps, but only making them available to the browser if the app is in dev mode.

[smessmer]

connnected: sbt/sbt-rjs#29

[mkurz]

+1