Option to reorder nodes, elements

[AndiMD]

Gmsh does not enforce consecutive numbering, but GmshDiscreteModel requires that. Gmsh has 2 builtin functions that seem to make it work.

[fverdugo]

Thanks @AndiMD !

Do you think this is somehow related to #3 ?

Cc @jesusbonilla

[AndiMD]

@fverdugo: Thanks for merging this. It allows loading .MED meshes created with Salome Platform (IMO the best OpenSource Geometry/Meshing software), since gmsh seamlessly converts it.
Unfortunately this does not improve the situation with #3. I will see if I can resolve this next, no promises though.

[jesusbonilla]

I have resolved issue of #3 in my fork. As @fverdugo suggested it is related with the local numbering used in Gridap vs Gmsh. Commit 6e70a00 implements a quick fix for it. We can merge it as is, or I can make any improvements required.