vis.revcorr.setRF

 SETRF - set the receptive field for the simulation

  [RF, TIMELAGS] = vis.revcorr.setRF(M, NUM_TIMESTEPS, DT)

  OUTPUTS:
   RF - the receptive field (MxMxNUM_TIMESTEPS), where the first two dimensions
        are space and the 3rd dimension is time.
   TIMELAGS - a vector of kernel times (going from 0 to positive), corresponding
              to the 3rd dimension of RF.

  INPUTS:
   M - the spatial dimension of the receptive field (result is MxM)
   NUM_TIMESTEPS - the number of time steps in the receptive field
   DT - the duration of each time step