Add custom dictionary support to FxCop

It's not a misspelling, if I say so.

On a related note I have this:

```
let GetProjectCodeAnalysisDictionary projectFile =
  XMLRead true projectFile msbuildNamespace "msbuild" ("msbuild:Project/msbuild:ItemGroup/msbuild:CodeAnalysisDictionary/@Include")
    |> Seq.head
```

To extract, from my Visual Studio project the file that is my custom dictionary. Not sure where this might belong but I'd be happy to put it there if you have an idea.