[TDF] Fixes to tutorials/dataframe/tdf013
[TDF] Fixes to tutorials/dataframe/tdf013

Now the TBrowser remains open after the event loop
and its directory contains the final result.
Many thanks to Andreas Weiden for the useful feedback!

karies/root,olifre/root,olifre/root,root-mirror/root,olifre/root,zzxuanyuan/root,zzxuanyuan/root,zzxuanyuan/root,karies/root,zzxuanyuan/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,karies/root,zzxuanyuan/root,olifre/root,zzxuanyuan/root,olifre/root,zzxuanyuan/root,karies/root,karies/root,zzxuanyuan/root,karies/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,zzxuanyuan/root,olifre/root,root-mirror/root,olifre/root,olifre/root,zzxuanyuan/root,zzxuanyuan/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root,zzxuanyuan/root,karies/root,olifre/root,root-mirror/root