update detector logic

Changed the way detectors draw noise from the PSD to follow the whittle likelihood. Noise is drawn in the frequency domain.

Updated parsing logic to support loading arbitrary TwoArmDetector configurations from an INI.

Updated how detector responses are returned to always pass a consistent shape, regardless of whether the long-wavelength approximation is employed or not. Shape will always be (len(freqs), len(azimuth)), which assumes azimuth, pole, and psi all have the same length.