Data enrichment

[mjpitz]

This will be a rather arduous task, but there's a lot of room for improvement on the extraction side of the world. For example, some languages support pulling in additional files. requirements.txt is one where it can load context from other requirements.txt files. Similarly, pom.xml can reference variables defined within properties files, build.gradle pairs with settings.gradle, and so on. And yet, we don't know the contents of these files until after they've been matched and the contents have been extracted.

We should find a way to support this pattern as it's somewhat common enough to pose some head aches.