[TDF] Add ctors to TSnapshotOptions
[TDF] Add ctors to TSnapshotOptions

ease aggregate initialisation and documentation by doxygen.

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