remove kiss_fft clash

- Dynamic adjustment of energy quantisation
- Psychacoustics
  * Error shaping within each band
  * Desisions on the rate
- Intensity stereo option (e.g. threshold)
- Dynamic (intra-frame) bit allocation 
- Joint encoding of stereo energy

- Encode band shape (or just tilt)?
- Make pitch less aggressive instead of using contraction?
- Make energy encoding more robust to losses?
- Revisit pulse spreading