add an import export class for the gmsh format

This issue was created automatically from an original Mantis Issue. Further discussion may take place here.

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add an import export class for the gmsh format

Gmsh is a pre / post / mesher available at: http://www.geuz.org/gmsh

The documentation is available here: http://www.geuz.org/gmsh/doc/texinfo/gmsh.pdf

And the file format is described at section 9.

YC