Restructure the detector module

bilby/gw/detector/__init__.py

bilby/gw/detector/detectors/CE.interferometer

bilby/gw/detector/detectors/ET.interferometer

bilby/gw/detector/detectors/GEO600.interferometer

bilby/gw/detector/detectors/H1.interferometer

bilby/gw/detector/detectors/K1.interferometer

bilby/gw/detector/detectors/L1.interferometer

bilby/gw/detector/detectors/V1.interferometer

bilby/gw/detector/interferometer.py

bilby/gw/detector/networks.py

bilby/gw/detector/noise_curves/AdV_asd.txt

bilby/gw/detector/noise_curves/AdV_psd.txt

bilby/gw/detector/noise_curves/Aplus_asd.txt

bilby/gw/detector/noise_curves/CE_asd.txt

bilby/gw/detector/noise_curves/CE_psd.txt

bilby/gw/detector/noise_curves/CE_wb_asd.txt

bilby/gw/detector/noise_curves/CE_wb_psd.txt

bilby/gw/detector/noise_curves/ET_B_asd.txt

bilby/gw/detector/noise_curves/ET_B_psd.txt

bilby/gw/detector/noise_curves/ET_D_asd.txt