Jet Energy Correction uncertainty groupings

[dwolfschlaeger]

This PR implements the possibility to define and add groupings of JEC uncertainties. In Artus a macro was added to read in the dictionary which assigns a list of individual uncertainties to a groupname. The TaggedJetUncertaintyProducer is now capable of adding these grouping names to the list of uncertainty names and calcules the resulting jet shifts by summing the member uncertainties up quadratically. This way a more elegant way to calculate also the "Closure" uncertainty was achieved (It is now defined as a grouping as well). Local tests prove the Producer to work as expected.

[jd550179]

I will look at this beginning next week