changing non_view_type to regular_type

- cosmetic : for clarity of the code.
arrays: rm has_view_type_tag & add_views

- has_view_type_tag mechanism was replaced by a decltype long ago.
Cleaning since it seems to work on all supported compiler now.

- removed add_views : not used any more.
arrays: remove .len (redundant)

.len -> .shape
with same syntax.
Made a few necessary corrections here and there.
arrays: rm tags file and some cleaning

- tags are defined in files, this impl/tags.hpp
was not needed any more.
- some code cleaning
arrays : add experimental array_const_view

- not completely clear how to
manipulate this alias, in particular when
matching template function
(and portability : require C++11 compiler).
arrays : rm linalg/determinant and inverse (links)

It is clearer to have only one file :
det_and_inverse.hpp
changed the included in tests.
arrays: rm debug code matrix_view_proxy_DEBUG.hpp

- used only for speed issue searching...
arrays: Remove dim0, dim1, .shape in various matrix object.

Not in the concept, not needed, just an annoyance.
replaced by free functions :
first_dim(A), second_dim(A), get_shape(A) and so on...
cmake : doc : correction boost link

readd the -L for boost_for_triqs link
in doc compilation
arrays: cleaning cuboid domain

- add one more constructor, clean constructor
- simplify foreach (use simple overload).
code cleaning

- TRIQS_MODEL_CONCEPT renamed : clearer for doc
- index_value_type : remove, useless...
arrays : correct deletion of std::swap for views

- forgot the bool flags, in case a weak view is involved.
gf : mesh now the class, not a trait.

simplify : mesh was a impl trait,
make it the class itself.
corrected the gf, tests and the cython.
gf: mesh. const_iterator and add cbegin

- for meshes :
clean concept w/ doc, add cbegin, and changed
iterator to const_iterator (more standard name).
work on doc