Reduce MATLAB boilerplate: PART VI

• Removing all 'spectral plotting' scripts, following development of the
  +plotDMFT module in DMFT-LAB
  > fast-forward of the relevant submodule

• Finally pruning RunningDMFT_refresh, for that runDMFT.refresh_line has
  been tested enough to supersede it.

—————————————————————————— Issue #2 - TODO —————————————————————————————

————> DMFT-LAB should soon extend the +plotDMFT module, allowing a deep
      refactor of both PlotDMFT and PlotMF scripts. At least making use
      of abstract functions for plotting observable lines, if not even
      implementing a totally generic interface for 2d-phase diagrams.