Fixed product loading

- Changed OSRelease not to read content file instead of os-release file in inst-sys (bnc#873366)
- Changed Product to use OSRelease.ReleaseInformation as :name instead of creating it from ReleaseName and ReleaseVersion, these are only used as fallback (bnc#873366)
- All constructors in Yast should be ...&^#^%#(*@!