Update README.md
Per Cureous suggestions, changed two items

AbstractElement<T>.DataType is now DatType
AbstractElement<T>.Data is now virtual
Merge remote-tracking branch 'upstream/master'

Conflicts:
	EvilDICOM.Core/EvilDICOM.Core.Tests/bin/Release/EvilDICOM.Core.Tests.dll
	EvilDICOM.Core/EvilDICOM.Core.Tests/bin/Release/EvilDICOM.Core.Tests.pdb
	EvilDICOM.Core/EvilDICOM.Core.Tests/bin/Release/EvilDICOM.Core.dll
	EvilDICOM.Core/EvilDICOM.Core.Tests/bin/Release/EvilDICOM.Core.pdb
	EvilDICOM.Core/EvilDICOM.Core.Tests/obj/Release/EvilDICOM.Core.Tests.csprojResolveAssemblyReference.cache
	EvilDICOM.Core/EvilDICOM.Core.Tests/obj/Release/EvilDICOM.Core.Tests.dll
	EvilDICOM.Core/EvilDICOM.Core.Tests/obj/Release/EvilDICOM.Core.Tests.pdb
	EvilDICOM.Core/EvilDICOM.Core.v12.suo
	EvilDICOM.Core/EvilDICOM.Core/bin/Release/EvilDICOM.Core.XML
	EvilDICOM.Core/EvilDICOM.Core/bin/Release/EvilDICOM.Core.dll
	EvilDICOM.Core/EvilDICOM.Core/bin/Release/EvilDICOM.Core.pdb
	EvilDICOM.Core/EvilDICOM.Core/obj/Release/EvilDICOM.Core.dll
	EvilDICOM.Core/EvilDICOM.Core/obj/Release/EvilDICOM.Core.pdb
	README.md