Adding all merged boost regions for 0-lepton channel

This adds all the merged boost regions to the 0-lepton channel, and foreshadows the structural change in the code I am proposing for both 0-lepton and 1-lepton channels to only add the necessary boost channels for each jet and b-jet multiplicity, rather than looping over all boost categories for all jet and b-jet channels.

@lvalery please check that the correct regions are added, at least for the default option (--doMergeBoost 1).