GRADLE-2688: Fix DefaultCachedModuleResolution.isDynamicVersion() - was always reporting 'true'
Removed unnecessary warning from User Guide: see http://forums.gradle.org/gradle/topics/there_is_no_gnu_unzip
Updated release notes and docs for publication validation stories
Validate that artifacts are not duplicates when publishing
- Also check that no declared artifact duplicates the generated meta-data file.
   - Didn't bother checking maven-metadata.xml (it would require a concerted effort to clash with this, including setting version = 'metadata')