OstapHEP/ostap: v1.7.1.0

v1.7.1.0 New features: add methods size_vars and array_vars for ROOT.TTree small adjustment for tree_reduce remove warnings for splot large improvements for tmva&chopping: allow ot specify working directory, etc... allow specification of training signal&background fractions for tmva&chopping disable ROC curved and ROC/AUX for old versions Backward incompatible: Bug fixes