Gradle 6.x support

[rpalcolea]

Gradle 6 introduces:

• warnings around the usage of compile and testCompile configurations as they will be removed in 7.0
• Gradle Fails on duplicates by default starting on 6.x. Before the default DuplicateStrategy was INHERIT which is to inherit the strategy from the parent copy spec, if any, or DuplicatesStrategy.INCLUDE if the copy spec has no parent.

Also upgraded the build-info-extractor plugin as current version is not Gradle 6.x compatible with the following error:

> org.gradle.api.publish.maven.internal.publication.MavenPublicationInternal.getPublishableFiles()Lorg/gradle/api/file/FileCollection;