add SM + flat-pT Z'

This contains a simple modification of the Top-Philic Zprime UFO model found in 1. The couplings of the Zprime have been adjusted to result in a 30% branching ratio into b-quarks, 30% into c-quarks, 10% each into u, d and s quarks and 5% each into electrons and taus.

In addition, the propagator of the Zprime has been modified such as to remove the resonance, generating a very flat pT spectrum of the resulting jets.

This model was originally created to be used for b-tagging at jet p_T >> 1TeV within the flavour tagging group.