Accounted for certain cases of catastrophic cancellation in quadraticRoots method.
Added additional tests for certain cases of catastrophic cancellation in quadraticRoots method.
Changed return value from null to zero-length array for cases where there are no real roots in quadraticRoots method.
Renamed class to be explicit about its purpose -- to count zero crossings (as opposed to, say, computing where the zero-crossings occur).
Renamed class to be explicit about its purpose -- to count zero crossings (as opposed to, say, computing where the zero-crossings occur).
Added cubic spline interpolation methods.  Also revised smoothing spline interpolation methods to revert to cubic spline interpolation when smoothing parameter input is zero.
Added cubic spline interpolation methods to WaveformUtilities class, plus some code cleanup.