Update SCons* files for Boost.Python wrappers

[pfernique]

SConscript files must be added in

• stat_tool/src/py/wrapper
• sequence_analysis/src/py/wrapper

And SConstruct files must be modified in

• stat_tool
• sequence_analysis

in order to incorporate new SConscript files

[pfernique]

See progress in branch new_python_api

[pradal]

Done for stat_tool in new_python_apibranch