Merge from master the commit 51021491ea9e6dc410cd38fca2a7b0ce6b984ae4

- improve all MinimumBuilder classes :
 - add a print level flag which can be used to control output
 - add a storage level flag which can suppress storing of MinimumState for each iterations
  (useful in problem with large number of parameters >~ 1000) to reduce memory
- add possibility to debug each iteration ny setting anew object MnTraceObject which will be called for every new iteration
- add an example class which histogram function value, edm, and parameters for each iteration
- add in Minuit2Minimizer possibility to enable these new options