Reading in already-calibrated listmode data causes other utils to fail

[jvavrek]

For example, in peakfinder.py, the auto-calibrator only looks for the raw edges:

def find_peaks(self, xmin=None, xmax=None, min_snr=2, max_num=40):
        """Find the highest SNR peaks in the data."""
        bin_edges = self.spectrum.bin_edges_raw
        bin_centers = self.spectrum.bin_centers_raw

As a workaround, one can set spec.bin_edges_raw = spec.bin_edges_kev, but we should think about a better solution in the future.

Tagging @markbandstra