Vtk export module for lattice models

[githubgrasp]

Introduce a vtk export module for lattice models which can plot mid-cross-sections of elements to show crack patterns.
Improved giveIPValue in lattice materials so that crack flag is given as scalar.
Fix some problems in latticeplasticitydamage with subincrementation and secant stiffness

[codecov]

Codecov Report

Merging #71 into master will increase coverage by 0.17%.
The diff coverage is 75.09%.

@@            Coverage Diff             @@
##           master      #71      +/-   ##
==========================================
+ Coverage   39.89%   40.06%   +0.17%     
==========================================
  Files        1241     1245       +4     
  Lines      124201   124629     +428     
==========================================
+ Hits        49547    49931     +384     
- Misses      74654    74698      +44

Impacted Files	Coverage Δ
...Materials/LatticeMaterials/latticebondplasticity.h	63.63% <ø> (ø)	⬆️
.../Materials/LatticeMaterials/latticelinearelastic.h	40% <ø> (ø)	⬆️
src/tm/Elements/LatticeElements/lattice2d_mt.h	38.46% <ø> (ø)
...Elements/LatticeElements/latticetransportelement.C	100% <ø> (ø)
...Elements/LatticeElements/latticetransportelement.h	7.69% <0%> (ø)
...lements/LatticeElements/latticestructuralelement.h	8.69% <0%> (-0.4%)	⬇️
src/oofemlib/vtkxmlexportmodule.h	11.76% <0%> (-65.51%)	⬇️
src/oofemlib/vtkxmllatticeexportmodule.h	0% <0%> (ø)
src/sm/Elements/LatticeElements/lattice3d.h	60% <100%> (+15.55%)	⬆️
src/oofemlib/vtkxmlexportmodule.C	55.43% <48.93%> (+1.73%)	⬆️
... and 36 more

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[githubgrasp]

Can these lattice related additions in the request be added? Happy to make extra changes if needed.