[NEW] Adding a new test case where the mixed formulation of the 3-D Poisson equation is solved with the Raviart-Thomas (face) elements

git-svn-id: https://elmerfem.svn.sourceforge.net/svnroot/elmerfem/trunk@6007 35e42291-063b-0410-a9f9-998d8d6728aa
[NEW] Adding a new test case where the mixed formulation of the 2-D Poisson equation is solved with the Raviart-Thomas (face) elements

git-svn-id: https://elmerfem.svn.sourceforge.net/svnroot/elmerfem/trunk@6008 35e42291-063b-0410-a9f9-998d8d6728aa