The airfoil interpolation process leads to a significant computational
hoverhead when the CL and CD coefficients must be calculated for each
section, as this process is O(N), N being the number of different
airfoils.

The basic interpolation as defined previously was creating a specific
Airfoil for each section, even when some contiguous sections shared the
same profile. This commit tries to limit the total number of Airfoils
generated by reusing the same object when it is possible.

Currently this only works by trimming airfoils when two contiguous
sections share the same profile. Ideally, we could also detect if the
same profile appears in non-contiguous sections (i.e. a blade with
sections (0012/0015/0012/0012) to reduce it even a bit more. However, as
the gain here is expected to be very limited, this final optimization
has not been implemented.