Add global QA

At this point, the most reasonable solution is to patch FairRoot (Otherwise it would be necessary to create child classes from FairRoot's singletons)

• FairTask.h : add method TList * GetTaskHistograms(), all histograms should be stored into private TList*
• FairRunAna.h : before finish all FairTasks are examined for nonzero GetTaskHistograms(), if there are any found, they are written into root file into their own branch (branch named after Fairtask/if no name, then untitled)