add IPython syle input

What do people think of adding IPython style input. So far I've just added a simple (no colours etc.) The new prompt behaves like this:

    [angus@angus-laptop ~]$ mathics
    
    Mathics 0.5.1dev
    on CPython 2.7.3 (default, Apr 24 2012, 00:00:54) 
    using SymPy 0.7.2-git, mpmath 0.17
    
    Copyright (C) 2011 Jan Pöschko
    This program comes with ABSOLUTELY NO WARRANTY.
    This is free software, and you are welcome to redistribute it
    under certain conditions.
    See the documentation for the full license.
    
    Quit by pressing CONTROL-D
    
    In[10]:= 1 + 2
    Out[10]= 3
    
    In[11]:= x^2
    Out[11]= x ^ 2
    
    In[12]:= 
    In[12]:= 
    In[12]:= 1
    Out[12]= 1

The reason this starts at 10 (not zero) is that some input is parsed during startup. We could obviously reset this to 0