Fixing DocumentationFile links, cleaning up csproj files

[shawncal]

Description

• The DocumentationFile paths were raising warnings because they were being set before the AssemblyName variable that they rely on.
• The 'RepoRoot' variable can be set in the common Directory.Build.props file, and then need not be set in all the csproj files individually
• Setting RootNamespace and PackageName to equal the AssemblyName, except in certain cases