Adding more interesting DumpXXX methods

- the bulk of this commit is about adding more interesting DumpXXX
methods, specifically: DumpObjects, DumpObject and DumpArray
- added DumpBlockedClrThreads
- now exposing an OutputWriter property on ClrMdPack
- cleaning up AssemblyInfo.cs
- simplified csproj build step for creating ArtifactsDir when it didn't
exist to just use BeforeBuild (not doing enough complexity to warrant
figuring out custom target right now)
- upgraded to ScriptCs.Contracts 0.4!
- removed unused usings from all files