MISC: Remove all files for actual sound generation

These will be used through the SoundTailor library.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
BUILD: Updated build files in order to use SoundTailor

DSP-related source files (filters, etc.) are no longer in the source
tree but may be used through the now external SoundTailor library.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
BUILD: Now using SoundTailor has a submodule

It is properly linked into tests as an external library.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
VCA: No longer using SoundTailor types

The need for an envelop generator section getter has been deleted.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
BUILD: Removed useless references to Soundtailor sources in openmini lib

Soundtailor is now used as an external library.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
DSP: Now using SoundTailor everywhere

Changes includes:
- replacing internal namespaces usage by soundtailor ones
- no longer using factories for filters and modulators
- new factory for generators using the ones from SoundTailor

Signed-off-by: Gama <misept.dieseneuf@gmail.com>