Add missing xml comments and fix style analyzer warnings

[nmetulev]

we discovered from #1443 that we have many missing xml comments that need to be added and several style issues that should be resolved.

[dotMorten]

Several warnings are created by auto-generated code. If you put <auto-generated> in the comment header, the compiler will ignore warnings in those files. Example of a typical header:

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
// *** Warning: Please do not edit as changes will be overwritten. This file is auto generated. ***
// </auto-generated>
//------------------------------------------------------------------------------

https://github.com/StyleCop/StyleCop/blob/3f701f549b5b2cd6dd8dda19866d083022b8da97/Project/Src/StyleCop.CSharp/FileHeader.cs#L104