Allow multiple Scalastyle files for a single project

[oharboe]

I'm using Scalastyle for a Chisel project(https://chisel.eecs.berkeley.edu/). Chisel is a DSL (domain specific language) for defining hardware on top of Scala.

There is a separate scalastyle-test-config.xml for src/test/scala and scalastyle-config.xml for src/main/scala. Separate scalastyle makes sense for Chisel DSL as it would e.g. be very annoying for a hardware language not to be able to use constants directly in test code, so the Chisel guy has expressed that by having to Scalastyle configuration files.

Could we have a way to set a separate Scalastyle fo src/test/scala and src/test/main?

[matthewfarwell]

At the minute the file is set at the project level. If you want to do a PR, we could discuss it...