feat(tracker): add menu to load instrument presets

The presets are embedded in the executable, so there's no additional files.

Closes #91

tracker/presets/snare6.yml

@@ -0,0 +1,48 @@
+name: Snare6
+numvoices: 1
+units:
+    - type: envelope
+      id: 1
+      parameters: {attack: 0, decay: 72, gain: 128, release: 72, stereo: 0, sustain: 0}
+    - type: send
+      id: 2
+      parameters: {amount: 128, port: 4, sendpop: 0, target: 1}
+    - type: envelope
+      id: 3
+      parameters: {attack: 0, decay: 64, gain: 128, release: 0, stereo: 0, sustain: 0}
+    - type: send
+      id: 4
+      parameters: {amount: 108, port: 0, sendpop: 0, target: 53}
+    - type: send
+      id: 5
+      parameters: {amount: 72, port: 0, sendpop: 1, target: 54}
+    - type: noise
+      id: 53
+      parameters: {gain: 64, shape: 32, stereo: 0}
+    - type: oscillator
+      id: 54
+      parameters: {color: 64, detune: 64, gain: 64, lfo: 0, phase: 0, shape: 96, stereo: 0, transpose: 64, type: 1}
+    - type: oscillator
+      id: 55
+      parameters: {color: 64, detune: 64, gain: 64, lfo: 0, phase: 0, shape: 96, stereo: 0, transpose: 76, type: 1}
+    - type: filter
+      id: 10
+      parameters: {bandpass: 0, frequency: 96, highpass: 0, lowpass: 1, negbandpass: 0, neghighpass: 0, resonance: 128, stereo: 0}
+    - type: addp
+      id: 11
+      parameters: {stereo: 0}
+    - type: addp
+      id: 12
+      parameters: {stereo: 0}
+    - type: mulp
+      id: 13
+      parameters: {stereo: 0}
+    - type: filter
+      id: 14
+      parameters: {bandpass: 0, frequency: 28, highpass: 1, lowpass: 0, negbandpass: 0, neghighpass: 0, resonance: 32, stereo: 0}
+    - type: pan
+      id: 15
+      parameters: {panning: 64, stereo: 0}
+    - type: outaux
+      id: 16
+      parameters: {auxgain: 0, outgain: 79, stereo: 1}