gf : improve error message
add header helper files
arrays : rm old array_proxy

- useless old draft
arrays: fix bug in ellipsis when it is of size 0

- a(1,ellipsis()) for a an array<T,1> e.g.,
was not compiling.
- also added const_iterator for range to allow simple code :
  for (auto i : range {3,6}) ....-> i = 3,4,5 as in python
arrays: clean h5 code

- c++11 cleaning, more doc.
- clean the array_stack and its doc.
arrays: add conj function for arrays/matrix and tests

- map conj (and extend it for integers).
arrays: clean cache, add traits ...

- also add simple c14 helpers ....
port to clang 3.4

- little narrowing details
Work on doc.
gf : fix bug in mesh_pt_generator

- in the default constructor, do not call the pointer
that may be null.
- appeared only in python (unused in c++), for new matsubara...
gf: update gf imfreq for g( om - nu) case

DRAFT : to be tested further...

- update gf<imfreq>
- write a specific mesh for matsubara frequencies
- now the cast series is :
  mesh_pt --> matsubara_freq --> complex<double>
- matsubara_freq is just the matsubara frequency
- arithmetic of the mesh_pt casted to matsubara_freq
- arithmetic of matsubara_freq is casted to complex, except + and -,
  which are kept as matsubara_freq.
- evaluator now accept : int, mesh_pt, and matsubara_freq
  for matsubara_freq : for negative omega, use conjugation
  for omega outside windows, evaluate the tail on omega.
- as a result : g( om - nu) where om, nu are 2 meshes points,
  is the extrapolation outside the grid if necessary.
- updated tests
- added evaluation for tail.