psx add more docu

[t-b]

image with different lo/hi values of deconv and other psx filter parameters

[t-b]

psx: filterLow and filterHigh, used in PSX_FilterSweepData, passed to FilterIIR. It's help says

Create bandpass and bandreject filters by specifying both /HI and /LO. For a bandpass filter, set fLow >fHigh, and for a band reject filter, set fLow < fHigh.

and we enforce low > high so this is bandpass filter. WP: https://en.wikipedia.org/wiki/Band-pass_filter.

psxdeconvFilter: lowFreq and highFreq used in PSX_DeconvoluteSweepData, passed to FilterFIR, and we enforce

ASSERT(lowFrac < highFrac, "Expected a low pass filter with lowFrac < highFrac")

so this is a low-pass filter. WP: https://en.wikipedia.org/wiki/Low-pass_filter

[t-b]

Already done in #2023.