Assorted developments (from VH(bb) analysis)

[adewit]

This adds some assorted developments that were introduced in the course of the VH(bb) analysis. Main changes:

• Adds ShapeUAsTH1F and ShapeDAsTH1F to the python interface
• Adds a method to swap up and down templates of a systematic uncertainty
• Adds a method to reverse the order of the bins when running PostFitShapesFromWorkspace
• Adds an option to save shapes for the sum of all categories in PostFitShapesFromWorkspace
• Adds a method to zero-out some bins in a distribution, while preserving the correct behaviour for the systematic uncertainties
• Introduces a small hack to handle the case where an input workspace has a RooDataHist and a RooHistPdf with the same name
• Suppresses some debug output in the card writer