Settle final convention for gf python constructors

Now n_points is used in all cases. beta, statistic are used
for Matsubara gfs. window = tuple is used for real-time and
real-frequency green's functions.

  modified:   doc/user_manual/data_analysis/fit/demo1.py
  modified:   doc/user_manual/data_analysis/fit/demo1_prepare.py
  modified:   doc/user_manual/data_analysis/fit/fit_test.py
  modified:   doc/user_manual/data_analysis/hdf5/tut_ex2.py
  modified:   doc/user_manual/data_analysis/plotting/example.py
  modified:   doc/user_manual/green/block.rst
  modified:   doc/user_manual/green/block/green_imfreq.py
  modified:   doc/user_manual/green/block/green_legendre.py
  modified:   doc/user_manual/green/block/green_pade.py
  modified:   doc/user_manual/green/block/green_refreq.py
  modified:   doc/user_manual/green/block/green_retime.py
  modified:   doc/user_manual/green/example.py
  modified:   doc/user_manual/green/full.rst
  modified:   doc/user_manual/green/impinbath.py
  modified:   doc/user_manual/green/legendre.py
  modified:   pytriqs/applications/impurity_solvers/ctqmc_hyb/ctqmc_solver.pyx
  modified:   pytriqs/applications/impurity_solvers/hubbard_I/solver_base.py
  modified:   pytriqs/gf/local/gf_imfreq.py
  modified:   pytriqs/gf/local/gf_imtime.py
  modified:   pytriqs/gf/local/gf_legendre.py
  modified:   pytriqs/gf/local/gf_refreq.py
  modified:   pytriqs/gf/local/gf_retime.py
  modified:   pytriqs/gf/local/refreq.pyx
  modified:   test/pytriqs/base/gf_base_op.py
  modified:   test/pytriqs/base/gf_init.py
  modified:   test/pytriqs/base/pade.py
  modified:   triqs/gf/local/pade.cpp
  modified:   triqs/gf/local/pade.hpp
  modified:   triqs/gf/retime.hpp