Height is now called elevation.
Fix installing the wav files.
lots of tidying up

- only read the audio files once
- parameters have actual number range and º units
Use the user's home directory (not mine).
Go backwards from 180 to 360 (sort of)
Fix the logging.
Put the diffuse HRTFs in a subfolder.
Download a bundle one of the HRTF DB archives.
Separate the HRTF from the FIR filter.

Diffuse is our current HRTF implementation. Need one for the HRTF DB
files too.
Add a basic HRTFDB implementation.
HRTFDB samples are bigger and need optimisations. Circular buffer for input and do all the processing in one go.
More optimising/tidying.
swap the correct way around.
Tidy tidy.