Fix titles in some plots of TrackerOfflineValidation/GlobalTrackVariables.
Improvements to plots of offline validation made by Eemeli Tomberg (chi2 and chi2 prob plots, save in .root format etc).
Merge branch 'fix-plot-titles_for72X' into improve-offline-validation_for72X
Merge pull request #4557 from tlampen/improve-offline-validation_for72X

Improve offline validation plots