schroedinger --plot option

Hi Ondrej,

to test the new live plotting, I have added the --plot option to schroedinger.py - it can now plot the convergence (or rather divergence :]) of DFT iterations, if matplotlib with GTKAgg and multiprocessing modules are available.

To all: standalone example is in examples/live_plot.py, just run:

$ python examples/live_plot.py

After the plotting is done the program waits on pause() - press any key to quit (Ctrl-C causes multiprocessing to hang, do not know why yet, and explicit kill is needed).

r.