DartIntegration: use EigenIntegration and small check for NaN values

[costashatz]

This PR adds the following to the DartIntegration:

• uses EigenIntegration when needed
• adds a small check for NaN values (so that Magnum asserts do not break the flow of the program)

[codecov-io]

Codecov Report

Merging #58 into master will decrease coverage by 0.32%. The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #58      +/-   ##
==========================================
- Coverage   74.77%   74.44%   -0.33%     
==========================================
  Files          21       21              
  Lines         880      900      +20     
==========================================
+ Hits          658      670      +12     
- Misses        222      230       +8

Impacted Files	Coverage Δ
src/Magnum/DartIntegration/Object.cpp	0% <0%> (ø)	:arrow_up:
src/Magnum/ImGuiIntegration/Context.hpp	87.5% <0%> (-12.5%)	:arrow_down:
src/Magnum/GlmIntegration/GtxIntegration.h	100% <0%> (ø)	:arrow_up:
src/Magnum/GlmIntegration/GtcIntegration.h	100% <0%> (ø)	:arrow_up:
src/Magnum/EigenIntegration/Integration.h	100% <0%> (ø)	:arrow_up:
src/Magnum/GlmIntegration/Integration.h	100% <0%> (ø)	:arrow_up:
src/Magnum/EigenIntegration/GeometryIntegration.h	100% <0%> (ø)	:arrow_up:
src/Magnum/ImGuiIntegration/Context.h	100% <0%> (ø)	:arrow_up:
src/Magnum/ImGuiIntegration/Context.cpp	83.13% <0%> (+0.09%)	:arrow_up:

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[mosra]

Merged as f55a61664532999bf91904b75d312252413af949 and 95d46a3c234423a70f482335db709e5b045fa857, thank you!