Fix periodic mesh

See merge request gmsh/gmsh!296

- use GEdgeLoop to compute signs in setBoundEdges()
- remove _orderMLines, so that createGeometry() does not modify the mesh anymore
- appply equivalement of _orderMLines only when creating compounds (for which the mesh needs to be reordered)

make gmm quiet byb default, and only warn if the iterative solver has not converged to the prescribed tolerance (fixes #749)

Better tex scaling

See merge request !299

- new option to disable forced font sizes (in most simple cases we actually want to not specify the font size, so that the font size from the .tex document will be used)
- new scaling option to scale the \includegraphics and the picture environment that positions the text to match a given width in mm: this allows to have readable text even if the font size is forced

CPEX 41 NGON, merged in CGNS 3.4.0, was removed in 3.4.1 and will only be reintroduced in CGNS 4.0.0. Should fix #748.

Change usage of CGNS_ROOT variable in CMakeLists

See merge request !298

# Conflicts:
#   doc/texinfo/opt_general.texi

Boundary angle plugin

See merge request !297

# Conflicts:
#   Plugin/CMakeLists.txt
#   Plugin/PluginManager.cpp

Rewrite node relocation in FixPeriodicMesh to simply map the master nodes on the slave surfaces, without doing the tricky "averaging" performed in contrib/HighOrderMeshOptimizer.

In periodic meshing of curves, don't assume that parametrizations of the master and slave curves are the same (unless the transform is not known), and proceed as for surfaces by explicitly transforming the master nodes and inverting the parametrization on the slaves.

(This will also allow to mesh bad geometries that are not exactly periodic - see #744)

Merge branch 'master' of http://gitlab.onelab.info/gmsh/gmsh

First stab at binary PLY reader

See merge request !294