Add a getFigs() method to allow users to personalise their plots.

Hi,

I tried last week to personalize a plot via the matplotlib methods, but I didn't found a way to get the figures objects of the plot. So I suggest to add this method to plot.py :

def getFigs():
 figs=[]
 for l in currLineRefs:
  l.update()
  figs.append(l.line.get_figure())
 return figs