Use median eye_position_data inter-sample interval for sample rate estimate
Use median eye_position_data inter-sample interval for sample rate estimate

Some PDS structs have trailing zeros in the eye_position_data matrix.
Therefore, we can't use end-start time in sample rate calculation. Jake
agreed that using 1/median(inter-sample time) was an acceptable
substitute.

physion/ovation-pldaps-importer,physion/ovation-pldaps-importer