Changed datatype of indices to int32.

buildout.cfg

setup.py

xbob/boosting/cpp/Machines.h

xbob/boosting/cpp/bindings.cpp

xbob/boosting/cpp/boosted_machine.cpp

xbob/boosting/cpp/lutmachine.cpp

xbob/boosting/cpp/stumpmachine.cpp

xbob/boosting/tests/test_machines.py

xbob/boosting/tests/test_trainer.py