Get rid of mesh kinds

There were three mesh kinds (half_bins, full_bins, without_last). These kinds
have been removed and only full_bins remain. So meshes have a point at the
beginning of the interval and at the end.
Merge branch '1.2-dev' of github.com:TRIQS/triqs into 1.2-dev

Conflicts:
	triqs/gfs/meshes/linear.hpp