Major overhaul for Amp Sim

Added "triggered" gate mode (detect pre-amp, operate post-amp).
Fixed incorrect filter sample rate when oversampling.
Fixed incorrect filter coefficient calculation resulting from above.
Fixed sketchy dynamics and filtering behaviour for Depth/Presence parameters.
Improved modulation scaling procedure.
Improved oversampling process.
Improved distortion process(es).
Improved internal gain staging.
Improved CPU efficiency.
Improved filter tuning.
Improved signal flow.
Improved comments.
Improved sound.