Merge pull request #362 from boegel/develop

bump version to v1.6.0.0rc1, update release notes
Merge branch 'v1.6.0.x' into develop
Merge branch 'develop' of github.com:hpcugent/easybuild-easyconfigs into develop
bump version to v1.6.0.0
bump version to v1.7.0.0dev