Add decfiles - Lb head backgrounds for Lb2LcLcn analysis

Adding 2 cocktail dec files for background studies of Lb2LcLcn analysis. Both files are from decays with Lb heads. One with only known decays/branching ratios and the other containing decays with unknown BRs.

Question: for event numbering the knownBKGs file has event number that showed no problem from running the the decay file convention parser given in the contribution guide: 15896010. I have then changed to 15896011 for the unknownBKGs file to keep them together although the parser complains about the lepton flag. Is this a reasonable thing to do?