ebur128: discard values < -200dBFS
move to new lv2_atom_forge_object
update screen-persistence default values (CLA suggestions)
phasewheel: FFT display 1.5 degree circle error-bar shadow
phase-wheel: decrease screen-persistence of low dB values (blue dots)
phasewheel: hue-spread over selected dB range, increase avail range to 80dB