Automatic frame edge finder

Added a new file get_wfm_windows.py containing a method to automatically find the edges of WFM windows. It find the valleys in the data corresponding to the delimitations between different frames, and performs for signal over background threshold analysis to detect the frame edges. This should be used as

frame_parameters = get_wfm_windows(workspace=ws, output_format="tof", plot="wfm_frames.pdf",
    win_threshold=0.20, xrange=[5000,72000], bg_threshold=0.02)

In addition, added a function in the wfm_processing.py file to compute the frame shifts automatically rather than using the Excel spreadsheet. This should be used as

frame_shifts = make_frame_shifts(-6630, get_frame_shifts(frequency_wfm_psc=70))