ENH: Cleanup of DPOAE calibration
ENH: Cleanup of DPOAE calibration

* Updated default parameters to ensure noise floor < 0 dB SPL using LBHB
acoustic system
* Don't allow user to specify equation for DP and DPOAE frequencies
* Increase output buffer size
* Show list of DP plots as data is acquired
* Add swag to plots (e.g. plot labels and grids)

bburan/cochlear