Pde dof instances

[TTitscher]

Solves #141

You can now create multiple dof instances at the node by

• constructing it with several instances
• allocating additional instances at the node
• allocating additional instances via MeshFem::AllocateInstances(dof, int) (probably most common way)

All the necessary changes were made to allow (cached) access to these instances at CellIpData level (= inside the integrands) with and optional last int parameter

• CellIpData::Value(dof, 2) (interpolate 2nd instance of dof)
• CellIpData::Value(dof) (interpolate default (0th) instance of dof)
• CellIpData::NodalValueVector(dof, 3) (vector of 3rd instance of nodal values for dof)

[codecov[bot]]

Codecov Report

Merging #230 into PDE_reviewed will increase coverage by 0.08%. The diff coverage is 100%.

@@               Coverage Diff                @@
##           PDE_reviewed     #230      +/-   ##
================================================
+ Coverage         84.32%   84.41%   +0.08%     
================================================
  Files               295      295              
  Lines             10676    10735      +59     
================================================
+ Hits               9003     9062      +59     
  Misses             1673     1673

Flag	Coverage Δ
#integrationtests	62.37% <84.21%> (-0.03%)	:arrow_down:
#unittests	87.84% <100%> (+0.09%)	:arrow_up:

Impacted Files	Coverage Δ
nuto/mechanics/mesh/MeshFem.h	100% <ø> (ø)	:arrow_up:
nuto/mechanics/elements/ElementInterface.h	100% <ø> (ø)	:arrow_up:
nuto/mechanics/tools/NodalValueMerger.h	100% <ø> (ø)	:arrow_up:
test/mechanics/elements/ElementFem.cpp	100% <100%> (ø)	:arrow_up:
test/mechanics/nodes/NodeSimple.cpp	100% <100%> (ø)	:arrow_up:
nuto/mechanics/cell/CellData.h	100% <100%> (ø)	:arrow_up:
nuto/mechanics/cell/CellIpData.h	100% <100%> (ø)	:arrow_up:
nuto/mechanics/iga/Nurbs.h	83.18% <100%> (ø)	:arrow_up:
nuto/mechanics/elements/ElementIga.h	60% <100%> (ø)	:arrow_up:
nuto/mechanics/elements/ElementFem.h	95.55% <100%> (ø)	:arrow_up:
... and 6 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 2556736...d456294. Read the comment docs.