refactor(core): Clean-up

- use "#pragma once" instead of the regular include guard
- fix errors and warnings reported by cppcheck

include/modules/script.hpp

@@ -1,5 +1,4 @@
-#ifndef _MODULES_SCRIPT_HPP_
-#define _MODULES_SCRIPT_HPP_
+#pragma once
 
 #include "modules/base.hpp"
 #include "services/command.hpp"
@@ -8,7 +7,7 @@ namespace modules
 {
   DefineModule(ScriptModule, TimerModule)
   {
-    const char *TAG_OUTPUT = "<output>";
+    static constexpr auto TAG_OUTPUT = "<output>";
 
     std::unique_ptr<Builder> builder;
 
@@ -25,12 +24,10 @@ namespace modules
     protected:
 
     public:
-      ScriptModule(const std::string& name);
+      explicit ScriptModule(const std::string& name);
 
       bool update();
       bool build(Builder *builder, const std::string& tag);
       std::string get_output();
   };
 }
-
-#endif