Fix: 0005037
Fix: 0006620
Fix: 0006178
Fix: 0008694

Remove support for wingraphviz. If people don't want to allow IIS to access cmd.exe, it would probably
be more sensible to write a dotnet wrapper around graphviz (e.g. http://implicitoperator.com/blog/2009/12/24/rendering-an-in-memory-graphviz-image-with-c.html)

However, that still needs a medium/full trust environment in asp.net I believe.

Windows users can install graphviz by downloading, the MSI from graphviz.org, allowing access to cmd.exe to the php application pool in IIS, and modifying the dot/neato paths.