[TDF] template TDFInterface on virtual base classes
[TDF] template TDFInterface on virtual base classes

...rather than on concrete TDataFrame{Branch,Filter}s.
This way there can be only three different specializations of TDFInterface

gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root