Wilson EM Plaquette action following 1205.6410

Following arXiv:1205.6410 this implements a Wilson plaquette gauge action with electric and magnetic part multiplied with (1+lambda) and (1-lambda), respectively. The corresponding input part for the gauge action looks like

    BeginMonomial GAUGE
      Type = Wilson
      beta = 5.60
      Timescale = 0
      Lambda = 0.5
    EndMonomial
 
where `Lambda` has only effect for `Type = Wilson`. Note that the plaquette value stored in `output.data` is the plaquette computed with `Lambda=0`.

This is not for merging yet, it needs to be tested and documented. But the HMC has acceptance. We also need probably a list of quantities to monitor.