Implement parts of EnvDTE.CodeModel
Update EnvDTE.CodeType unit tests.

Return correct value for InfoLocation on EnvDTE.CodeType.
Update EnvDTE.CodeVariable tests.
Implement more EnvDTE.CodeClass2 tests.
Implement EnvDTE.CodeProperty2
Update EnvDTE.CodeParameter2 tests.
Update EnvDTE.CodeFunction tests.
Update tests for EnvDTE.CodeTypeRef2
Update tests for EnvDTE.CodeInterface
Update tests for EnvDTE.CodeStruct.
Update tests for EnvDTE.CodeAttribute2.
Update unit tests for EnvDTE.CodeDelegate.
Only use NRefactory in EnvDTE.CodeType.
Move test to correct namespace.
Update tests for EnvDTE.CodeNamespace.
Implement Namespace for EnvDTE.CodeType.
Add IsPartial flag to indicate class is partial in NRefactory type system.

A single C# class with the partial keyword but without any other parts
can now be identified.
Return correct EnvDTE.CodeClass2.ClassKind for a partial class.
Use separate flags for partial methods and type definitions.
Add IsPartial property to ITypeDefinition.