Fix documentation and add warning

[Psirus]

• Activate -Wdocumentation warning; fixes #21
• fix the resulting warnings
• remove TimeControl class, since its not used and had a lot of warnings :)

[codecov[bot]]

Codecov Report

Merging #211 into PDE_reviewed will decrease coverage by 0.3%. The diff coverage is 100%.

@@               Coverage Diff                @@
##           PDE_reviewed     #211      +/-   ##
================================================
- Coverage         68.13%   67.82%   -0.31%     
================================================
  Files               315      312       -3     
  Lines             12241    12089     -152     
================================================
- Hits               8340     8199     -141     
+ Misses             3901     3890      -11

Impacted Files	Coverage Δ
...oncrete/collision/collidables/CollidableWallBase.h	100% <ø> (ø)	:arrow_up:
...ete/collision/collidables/CollidableParticleBase.h	100% <ø> (ø)	:arrow_up:
...ete/collision/collidables/CollidableWallPhysical.h	33.33% <ø> (ø)	:arrow_up:
src/metamodel/NeuralNetwork.h	0% <ø> (ø)	:arrow_up:
...c/mechanics/constitutive/ModifiedMisesStrainNorm.h	90.74% <ø> (ø)	:arrow_up:
...e/collision/collidables/CollidableParticleSphere.h	100% <ø> (ø)	:arrow_up:
...ete/collision/collidables/CollidableWallCylinder.h	0% <ø> (ø)	:arrow_up:
src/mechanics/integrands/GradientDamage.h	100% <ø> (ø)	:arrow_up:
...ics/integrationtypes/IntegrationType3D4NGauss1Ip.h	0% <ø> (ø)	:arrow_up:
src/visualize/UnstructuredGrid.h	100% <ø> (ø)	:arrow_up:
... and 58 more

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