Templates, flexible envelopes, improved customization

• New: Add waveform_templates and effect_templates section for reusable abstractions.
• New: Add LfSource::Semitones to convert values in semitones to frequency ratios.
• New: Add OffVelocitySet, OffVelocity and KeyPressureSet live parameters.
• Improvement: Envelopes support automations.
  • Change: The parameters amplitude and fadeout are mandatory parameters.
• Improvement: Customize velocity sensitivity.
  • The envelope's amplitude parameter controls how the waveform's amplitude depends on the velocity or any other control value.
• Improvement: Customize damper-pedal / fadeout behavior.
  • The envelope's fadeout parameter controls how the waveform is faded out depending on the damper pedal state or any other control value.
• Improvement: Customize pitch-bend wheel behavior.
  • The current pitch-bend value is queryable via the PitchBend live parameter.
  • Use LfSource::Semitones to calculate the correct frequency depending on the pitch-bend value.
• Improvement: Control magnetron volume via Velocity events (CCN 7, configurable).
• Change: Rename from/to in Linear and Controller to map0/map1 to better explain the mathematical behavior.