feat(plot): lock axes and calculate marker levels in dB

c/set-protocol/tests/fixtures/plot-v1.json

@@ -20,6 +20,9 @@
     {"name":"ticks","op":5,"input":[100,800],"output":[20]},
     {"name":"negative_delta","op":6,"input":[10,0,1],"output":[-10]},
     {"name":"milliseconds","op":6,"input":[0,0.01,1000],"output":[10]},
+    {"name":"db_gain","op":7,"input":[1,10],"output":[20]},
+    {"name":"db_attenuation","op":7,"input":[10,1],"output":[-20]},
+    {"name":"db_zero_reference","op":7,"input":[0,1],"output":null},
     {"name":"zero_range","op":2,"input":[1,1,1,0],"output":null},
     {"name":"zero_pixels","op":4,"input":[0,1,0,0,1,0],"output":null},
     {"name":"bad_viewport","op":0,"input":[0,0,0,1,2,1,0,0,0.5,0.5],"output":null}