Before encoding a compoundBlob we create a compoundBlobStruct and
encode that instead.
After decoding we check if the value is a compoundBlobStruct and if so
we convert it to a compoundBlob.
Fixes#455, #165
Ref Values now have a TargetRef() method that returns the ref.Ref of
the target the Value is referencing.
Note: This is a breaking change. In old code the Ref() of the Value was
the Ref of the underlying target.
Fixes#464
Erik Arvidsson