* Cleaned up copyright notices in AssemblyInfo.cs's
* Added Copyright headers to a bunch of files missing them
* Replaced several common string instances with a static constant to prevent reallocation of the same strings thousands of times. "" -> String.Empty is the first such candidate.
Note this has lead to a big flat project, but I think a lot of the files we most likely don't even use any longer. And others belong in other projects/namespaces anyway.