Externalize samples testing infrastructureThis change replaces UserGuideSamplesRunner with an external librarycalled sample-check. Sample discovery, execution, and normalizationis delegated to this library, with some custom normalizers remainingin the Gradle codebase.Samples output has become co-located with the sample code. Samples testsmust be run with Java 8+.
Separated classes ouput directory from resources output directory. This requires a code review but I preferred to check in the changes. Updated the documentation, user guide and tests accordingly. New property is called resourcesDir (I somewhat don't like the name but that's what we agreed with Adam).