Make digraph creation case insensitive

[neraath]

We have a solution that has > 1500 projects that we're trying to assess how to break up. Due to the nature of how the solution and references are put together, there are some case differences. Windows doesn't care when compiling, but when doing the analysis, I find duplicate entries for the same csproj in the digraphs being generated.

This fix will allow digraphs to be generated with case insensitive comparison and meeting our needs.