Update Global/VisualStudio.gitignore

Add trailing slashes to folders, RS rule comment, remove dupes. 

NB: quite a bit of overlap here with "CSharp.gitignore" .. but given that GitHub's .gitignore deployment mechanism only supports a single file, perhaps this isn't a bad thing (C# vs general VS). I've also added additional entries to the C# version (subject to acceptance) that not included here.