Fixing imaginary time GF
Fix the tail

  modified:   pytriqs/base/gf/local/descriptors.py
  modified:   pytriqs/base/gf/local/gf_imfreq.py
  modified:   pytriqs/base/gf/local/gf_imtime.py
  modified:   pytriqs/base/gf/local/tail.pxd
  modified:   pytriqs/base/gf/local/tail.pyx
  modified:   triqs/gf/local/tail.hpp
  modified:   triqs/gf/test/gfv2.output
Fix Fourier transforms

  modified:   triqs/gf/local/fourier_base.cpp
  modified:   triqs/gf/local/fourier_base.hpp
  modified:   triqs/gf/local/fourier_matsubara.cpp
  modified:   triqs/gf/meshes/linear.hpp
Improve doc for MC class

Removed references to mc_sign_type and mc_weight_type that are
now obsolete.

  modified:   applications/standalone/ising1d/moves.hpp
  modified:   doc/developer_manual/conf.py.in
  modified:   doc/developer_manual/mctools/ising.rst
  modified:   doc/developer_manual/mctools/overview.rst
  modified:   doc/developer_manual/mctools/reference.rst