BusModes IntEnum added to bus

get() added to bus mode mixin, returns the current bus mode.

added support for setting bus mode by dict
fixed bug in apply where bool parameters weren't being applied.

bus modes added to all 3 example configs.

test_config added to unit tests.

configs/basic/example.toml

@@ -10,14 +10,13 @@ audibility = 3.2
 
 [strip-2]
 label = "VirtStrip0"
-bass = -3.2
-mid = 1.5
-treble = 2.1
 
 [bus-0]
 label = "PhysBus0"
 mute = true
+mode = "composite"
 
 [bus-1]
-label = "PhysBus1"
+label = "VirtBus0"
 mono = true
+mode = "amix"