Replace magic numbers, fix bindings localization

Replace magic numbers with constants and centralize settings update counters. Rename actions manifest localization from "en" to "en_US" (Thanks Ykeara)

src/tabcontrollers/AudioTabController.cpp

@@ -169,19 +169,7 @@ void AudioTabController::eventLoopTick()
         return;
     }
 
-    // 89 was chosen because it's a prime number (to reduce overlap of
-    // simultaneous settings updates).
-    // Actual rate of updates is 89 * vsync (~11ms)
-    // Values chosen based on update speed priority
-    // Values in other tabs are as follows (avoid using same values):
-    // AccessibiltyTabController: 151
-    // ChaperoneTabController: 101
-    // MoveCenterTabController: 149
-    // ReviveTabController: 139
-    // SettingsTabController: 157
-    // SteamVRTabController: 97
-    // UtilitiesTabController: 19
-    if ( settingsUpdateCounter >= 89 )
+    if ( settingsUpdateCounter >= parent->k_audioSettingsUpdateCounter )
     {
         if ( m_micProximitySensorCanMute )
         {