adjusted accuracy constants,

relabeled minAfStrike and maxAfStrike to leftCoreStrike and
rightCoreStrike to reflect that this is the effective
region outside which extrapolation is done, which may be smaller than
the actual arbitrage free region,

explicitly call the helper functions after zero search, because it
may not be ensured by the solver that the last function evaluation is
done at the solution
trim precondition check
corrected arbitrage check w.r.t. right strike
added test case for Kahale smile section,

removed code for debug outputs