[Hotfix] Particle on edge error

[bodhinandach]

Describe the PR A nudge is implemented inside is_point_in_cell(), shifting the relative coordinate using std::numeric_limit<double>::epsilon(), if a particle is lying exactly on element edge.

Related Issues/PRs Fix #656.

[codecov[bot]]

Codecov Report

Merging #657 into develop will decrease coverage by 0.00%. The diff coverage is 91.67%.

@@             Coverage Diff             @@
##           develop     #657      +/-   ##
===========================================
- Coverage    96.56%   96.55%   -0.00%     
===========================================
  Files          122      122              
  Lines        25316    25336      +20     
===========================================
+ Hits         24444    24463      +19     
- Misses         872      873       +1     

Impacted Files	Coverage Δ
include/cell.tcc	87.46% <81.82%> (-0.04%)	:arrow_down:
tests/cell_test.cc	100.00% <100.00%> (ø)

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[bodhinandach]

@ezrayst Is this what you want to see:

Without correction (develop):

With correction (this branch):

[ezrayst]

@bodhinandach, in the results you show with 3x3 material points, why does the error happen when the last column of the material points hit the edge (not the first column)? I feel that the problem happens if the material all the material points in that element lie on the edge - do you agree with me?