make ResetDatabase work for string options


git-svn-id: https://geuz.org/svn/gmsh/trunk@18373 59c8cabf-10d6-4a28-b43f-3936b85956c4
credit Hang Si


git-svn-id: https://geuz.org/svn/gmsh/trunk@18374 59c8cabf-10d6-4a28-b43f-3936b85956c4
git-svn-id: https://geuz.org/svn/gmsh/trunk@18375 59c8cabf-10d6-4a28-b43f-3936b85956c4