Limit visibility updates

Prevent visibility updates to occur for inactive modules.
Check active modules and subscribe to only those events.

include/modules/sway/bar.hpp

@@ -37,6 +37,7 @@ class BarIpcClient {
   void onModeUpdate(bool visible_by_modifier);
   void onUrgencyUpdate(bool visible_by_urgency);
   void update();
+  bool isModuleEnabled(std::string name);
 
   Bar& bar_;
   util::JsonParser parser_;