title: Tell IntelliJ IDEA I want library sources for a Scala project after the fact
body: <p>I have created an IntelliJ IDEA Scala project from existing <code>built.sbt</code>. I had not checked the auto-import and download-sources boxes. I regret. Can I tell IDEA that I do want these two options, especially download-sources, without having to delete and re-create the project?</p>