Initialise nodal, multimaterial properties

[thiagordonho]

Implement the initialisation of all the properties in the nodal properties pool and call this function from the MPMExplicit. The following describe the rational behind the initialise_properties function:

• Iterates over all properties in the std::map of properties.
• Creates a null matrix of the same size of the property's Eigen::Matrix
• Assign the null matrix to the entire property's Eigen::Matrixusing the previously implemented assign_property in NodalProperties.

After proper implementation, call initialise_properties() at the beginning of the computational step loop.

This PR is related to the RFC #636 . A reset to zero of all the properties' values is expected with the changes in this PR. This initialisation is necessary in order to recalculate the multimaterial properties with every step in the Contact Algorithm.

[codecov[bot]]

Codecov Report

Merging #643 into develop will decrease coverage by 0.00%. The diff coverage is 96.30%.

@@             Coverage Diff             @@
##           develop     #643      +/-   ##
===========================================
- Coverage    96.56%   96.56%   -0.00%     
===========================================
  Files          122      122              
  Lines        25175    25200      +25     
===========================================
+ Hits         24308    24332      +24     
- Misses         867      868       +1     

Impacted Files	Coverage Δ
include/mesh.h	100.00% <ø> (ø)
include/solvers/mpm_explicit.tcc	64.19% <50.00%> (-0.44%)	:arrow_down:
include/mesh.tcc	83.95% <100.00%> (+0.06%)	:arrow_up:
src/nodal_properties.cc	100.00% <100.00%> (ø)
tests/mesh_test_2d.cc	98.44% <100.00%> (+<0.01%)	:arrow_up:
tests/mesh_test_3d.cc	98.67% <100.00%> (+<0.01%)	:arrow_up:
tests/nodal_properties_test.cc	100.00% <100.00%> (ø)

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[thiagordonho]

@kks32 , how can I fix this code coverage issue?