Expand .gitignore cases
Expand .gitignore cases

Update to .gitignore to exclude places that are only populated by
editing and builds and never carried in the repository.  Added more
comments to make the principle clear, with a little redundancy in the
case of Visual Studio artifacts.

apache/incubator-corinthia,apache/incubator-corinthia,apache/incubator-corinthia,apache/incubator-corinthia,apache/incubator-corinthia,apache/incubator-corinthia,apache/incubator-corinthia