Add decfiles and options files to generate Hard-QCD background candidates

This MR includes two different decay files to generate stable charged particles with high p_T arising from Hard-QCD interactions. The difference between the two is on the minimum transverse momentum of the QCD subprocess and the generated candidate. The generator-level efficiencies are \sim 0.6\% and the time to generate an event is smaller than one minute.

More information about the goal of this addition can be found at LHCb-QEE/WmassMeasurement#503.