Add band-pass filter docs

document `bandf` and `bandq` band-pass filter settings
add high-pass filter doc

document `hresonance` and `hcutoff` like, taken from `resonance` and `cutoff`
add crush and coarse doc

document `crush` and `coarse` parameter values
Merge pull request #44 from lennart/master

Added docs for new filters/effects (bpf, hpf, coarse and crush)