Changed VersionLister.getVersionList() so that it pushes versions (and candidate locations) to the provided result objects.
Renamed VersionList and VersionLister.getVersionList().
Changed ChainedVersionLister so that it does not ignore unexpected failures.
Include maven-metadata.xml as a candidate location in the 'snapshot not found' exception message.
Added some test coverage for error handling when things go wrong listing versions.
Updated release notes.