Gmsh reader

As the .msh file does not differentiate lower-dimensional blocks and sidesets, we need to change the Gmsh format (and the Moose's reader).

This will allow us for example to create 2D fractures in a 3D rock matrix.

Manual change of the .msh file

Find in the file the paragraph that looks like this :

$PhysicalNames
4
2 1 "fracs"
2 3 "top"
2 4 "bottom"
3 2 "volume"
$EndPhysicalNames`

You want your group "fracs" to be a lower-dimensional block instead of a sideset so just write our keyword lower_dimensional_block at the end of this line, like this :

$PhysicalNames
4
2 1 "fracs" lower_dimensional_block
2 3 "top"
2 4 "bottom"
3 2 "volume"
$EndPhysicalNames

The group "fracs" will now be recognized as a block like the group "volume".

##Moose's new Gmsh reader

###File

gmsh_io.C

###Usage

When the mesh is loaded on peacock, it will recognize the groups tagged with lower_dimensional_block as blocks.