Fix XML documentation errors

I have a medium-size open-source project in C#. While all the non-intuitive areas are XML documented, many public classes, methods, and properties are lacking XML documentation elements. You task is to add docs where appropriate (~1,000), and "#pragma warning disable 1591" the rest (~1,200). Details: Fork the 'appveyor' branch to perform your work. Ensure that your text editor is NOT set to 'reformat' code, whitespace, or line endings; your commits must be *clean*, only showing documentation insertions. [login to view URL] The full list of warnings generated by the project can be found here: [login to view URL] LegacyWatermark and InteropServices or Extern declarations do *not* need to be documented, they can be pragma disabled. There are ~100 pages of reference documentation at [login to view URL] if you have questions. As nearly all plugins follow the same structure, however, I don't think there are many elements that will require lookup. Correct spelling and grammar required.