GRADLE-3170 Idea gradle plugin generates wrong sources jar for multi artifact dependencies

Add tests and a fix for issue where Ivy dependencies do not have sources attached correctly.

See http://forums.gradle.org/gradle/topics/idea_gradle_plugin_generates_wrong_sources_jar_for_multi_artifact_dependencies
Extract interface out of AuxiliaryArtifactMatchStrategy
Some cleanup on AbstractSourcesAndJavadocJarsIntegrationTest

- remove reduntant test
- fix some formatting
mention Gregs pullrequest in release notes