git-svn-id: https://geuz.org/svn/gmsh/trunk@18033 59c8cabf-10d6-4a28-b43f-3936b85956c4
FormulationOSRC into CoupledFormulation frame work -- much clear

git-svn-id: https://geuz.org/svn/gmsh/trunk@18034 59c8cabf-10d6-4a28-b43f-3936b85956c4