Display shaker locations returned by SHAKER_LOCATOR
hp = plot_shaker_locations(fem,shaker)
PLOT_SHAKER_LOCATIONS displays the shaker locations returned by SHAKER_LOCATOR. One plot will be created per index in SHAKER. PLOT_SHAKER_LOCATIONS uses VTKPLOT to display the plots.
FEM is an IMAT_FEM on which to plot the shaker locations.
SHAKER is the Shaker structure returned by SHAKER_LOCATOR.
HP is an cell array of IMAT_VTKPLOT objects pointing to each plot created.