Add extractor in utility
Fix python object extraction in improved dict

  modified:   triqs/python_tools/improved_python_dict.hpp
Added gf in triqs/CMakeLists.txt
first draft of expansion
detil
starting gf::local
saving work
saving work
with shared aux Ptr
before splitting gf
saving intermediate work
added first test of gf
split class in gf_impl
added first gf test
various little details. testing slice, tail, etc...
saving current state...
simplified gf.hpp
working on gf local
working on gf local prototype
work in progress on gf. Need : tests, and wrap grid point in general, and 1/Matrix expressions