Fix a misplaced NOT in FindCompilerCheck.cmake

  modified:   cmake/FindCompilerCheck.cmake
arrays/vector: little correction on = std::vector

- forgot the borrowed flag.
simple consequence of the weak view change.
uility : add foreach_enumerate

- to be tested
gf : add nearest_point for krylov

To be cleaned, it is redundant.
I put it here to make the krylov app compile properly
utility : add tuple_serialize code
cmake: add macro to fix rpath to triqs install

- to be tested on mac
arrays: fix a missing include in eigenelements
utility : add printing of a tuple

- << tuple now works, with a default version.
Useful for debugging
icc : workaround macro was not set in the config.h

- forgot to declare one cmake var.
- test can now be not compiled (Build_Triqs_General_Tools_Test had no
  effect)
cmake. add system to boost detection
added two little tests ...

- draft of reinterpret_array_view and immutable_diagonal_matrix
gf: draft of iterator on gf blocks ...

 - to be completed
- missing cbegin et al, pb with for(auto & g : ...)
because it returns a view...
doc: fix the MathJax option

- if Mathjax is detected, use it by default,
it not do not use it by default but allow the user
to provide the path.
[API BREAK] gf : rename namespace gf->gfs

- necessary otherwise the class gf and the namespace have
the same name, leading to some confusion, and need to qualify
some functions (specially on gcc).
Same naming conventions as arrays.
[API BREAK] gf : mesh_pt into []

- All access to grid is now using the [] operator.
() always returns const, and is an evaluation over the domain.

- Now :
 * () is always a call to evaluator (or a lazy expression).
 * mesh_pt accepted by [] , both const and non const,
and not by ().

- Ported the libs (fourier et al.) but this break API.
[API BREAK] rename directory gf -> gfs
gf: fix upper bound in out of bounds check in linear mesh
Merge remote-tracking branch 'triqs_lib/master'

Conflicts:
	test/triqs/gf/gf_retw.cpp
gfs: scalar for two-real_times