add MetricBasis


git-svn-id: https://geuz.org/svn/gmsh/trunk@17930 59c8cabf-10d6-4a28-b43f-3936b85956c4
iOS: fix alert on error


git-svn-id: https://geuz.org/svn/gmsh/trunk@17931 59c8cabf-10d6-4a28-b43f-3936b85956c4