[Halld-offline] DSelector Bugs Now Fixed

[Paul Mattione]

A series of problems with the DSelector have now been fixed.  If you "git pull" to update your gluex_root_analysis repository, you can now:

1) Run over TChains: Some channels crashed before, but not others.  They should all work now. 
2) Create output clones of the input tree (with e.g. cuts placed): Before, it crashed if you were running over a TChain when doing this. 
3) Create and fill custom branches on this output clone tree: Some users were experiencing crashes here as well. 

If you run MakeDSelector again, you'll get examples on how to create and fill custom branches. 

Sorry it took so long to get around to fixing these problems.  Thank you all for your patience. 

 - Paul