Initial version of TBranchPrecisionCascade Print

[genevb]

This very basic version of Print() allows one to see which branches are in the PrecisionCascade files. I expect there is considerable room for improvement to this function, but this initial version is already helpful. The printing includes the detail of whether each branch's PrecisionCascade levels extend to the level of the PrecisionCascade file under examination. In other words, if one branch is saved with 3 levels (which may be 2 + 1 residual, or 3 + 0 residual) and another branch is saved with 2 levels (either 1 + 1 residual, or 2 + 0 residual), then the branches with only 2 levels will not show up in the third file, which is good to know.

In the example below, the branches' compression configuration levels (from a TTree name "PicoDst") were set as:

Track.mGMomentumX -> 2 + 0 residual
Track.mGMomentumY -> 1 + 1 residual
Track.mGMomentumZ -> 2 + 1 residual

And here's what the Print() as implemented in this PR helpfully shows:

root -l -b -q gp_all.root.55_precisioncascade_1.root -e 'PicoDst_pc1->Print()'

Attaching file gp_all.root.55_precisioncascade_1.root as _file0...
(TFile *) 0x7fafa20d7560
TTreePrecisionCascade: PicoDst_pc1 TTree uniqueID: 1 TTree pid: 1 level: 1
TBranchPrecisionCascade: Track.mGMomentumX level: 1 Basket Size: 163858
TBranchPrecisionCascade: Track.mGMomentumY level: 1 Basket Size: 685917
TBranchPrecisionCascade: Track.mGMomentumZ level: 1 Basket Size: 172095

root -l -b -q gp_all.root.55_precisioncascade_2.root -e 'PicoDst_pc2->Print()'

Attaching file gp_all.root.55_precisioncascade_2.root as _file0...
(TFile *) 0x7fe4a48f1d90
TTreePrecisionCascade: PicoDst_pc2 TTree uniqueID: 1 TTree pid: 1 level: 2
TBranchPrecisionCascade: Track.mGMomentumZ level: 2 Basket Size: 567419