Add python output support to the statistics package!

Add python output support to the statistics package!

base/statistics.cc:
base/statistics.hh:
    -  add python output support to the statistics package
    -  each statistic type has a python() member function that takes
    a Python object to which the stat will output it's python
    representation
    -  add getStatData hack so that the StatData pointer can be looked
    up by the proxies with their opaque pointer to the stat they're
    proxying for.  This is necessary because the proxy really proxies
    for the bin and not the stat.  Be nice to figure out how to get
    rid of it.  The hack is used so that the str() function of a
    proxy can properly name itself.
    -  To print formula stats, every stat has a str() function that
    converts that stat to a string that python can execute to get
    a value.
test/Makefile:
    add python stuff
test/stattest.cc:
    add more tests and test python support

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extra : convert_revision : 513814ab0a125606897f2c57dccdf22879032ef9