Split Integrals constructor to accept polygon and polygons.
Add operator+(Integrals, Integrals).
Make sure extrusion extraction for integral calculation throws in invalid case.
In SupportSpotsGenerator there is a need to compute integral over
extrusions.
The mentioned function is slow for this use case. As it solves a harder
problem.
It is better to iterate the extrusion lines directly.
There was a test that relied on randomness and also checked the result
with very hight precision. That led to a failed test once upon a time.
Now the checking is more benevolent (it should be, as the code is
not expected to be precise) and also the randomness is removed.
SupportSpotsGenerator originally used a heuristic formula. Current
formula is properly derived using known properties of
second moment of area. Several tests of this formula are added.
