Transforms to clean up

[Quefumas]

1. In what module should they appear?
2. How should they be named?
3. What are the proper arguments?
4. At least some superficial testing

These are the problem ones:

• [x] Fade - enable choosing curves? How wide should the dB range be? Should we enable determining is_in argument from multiplication direction?
• [x] Convolution - test. Also what does it mean to convolve two stereo signals together?
• [x] Raw signal - test.
• [x] Average_samples - what is the proper name. Also overlaps FIR.
• [x] AmpFreq - what is the proper name?