Component Selection vs ROOT

It seems there is a bug in ROOT that doesn't allow to select components of a PDF containing a comma. This is problematic when plotting complicated PDFs, since we automatically add the comma to build the PDF name (I can write an MWE for you to understand the problem, but that is something for tomorrow).

@jeschle @flionett @cmarinbe @matzeni I propose to change the comma for a semicolon. I will make a PR if everybody agrees.