Fix a couple of tutorials.
Merge branch 'master' of https://root.cern.ch/git/root
Update cocoa tutorials to make it possible run them all in one session (before

they were using the same color indices for custom colors and this was not good at all).
Also, make these tutorials look more ... modern (?) and reasonable, add some primitive error handling at least.
FindFreeCustomColorIndex - scan gROOT's color indices and search the first free (in some hardcoded range).
Remove forgotten printout
Adding copy constructors to build models using python more robustly.
bugfixes. Fix HF for models without any nuisance parameters.
Bugfix copy constructor for non-counting models.