Update copyrights for DataGridExtensions and TomsToolbox

doc/third-party-notices.txt

@@ -291,10 +291,11 @@ END OF TERMS AND CONDITIONS
 License Notice for Data Grid Extensions (part of ILSpy)
 ---------------------------
 
-https://github.com/tom-englert/DataGridExtensions/blob/master/License
+https://github.com/dotnet/DataGridExtensions/blob/master/License
 
 The MIT License (MIT)
-Copyright (c) 2012-2019 tom-englert.de
+Copyright (c) .NET Foundation and Contributors
+All Rights Reserved
 
 Permission is hereby granted, free of charge, to any person obtaining a copy 
 of this software and associated documentation files (the "Software"), to deal 
@@ -504,8 +505,8 @@ License Notice for Tom's Toolbox (part of ILSpy)
 https://github.com/tom-englert/TomsToolbox/blob/master/LICENSE
 
 The MIT License (MIT)
-
-Copyright © 2012-2019 tom-englert.de
+Copyright (c) tom-englert.de
+All Rights Reserved
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal