Default (XML) electrical system: fix leaks

Ensure shutdown of the electrical system actually cleans up components.

Fixes some leaks and dangling properties on reset.

src/Systems/electrical.cxx

@@ -359,7 +359,9 @@ FGElectricalSystem::FGElectricalSystem ( SGPropertyNode *node ) :
 }
 
 
-FGElectricalSystem::~FGElectricalSystem () {
+FGElectricalSystem::~FGElectricalSystem()
+{
+    SG_LOG(SG_SYSTEMS, SG_INFO, "Destroying elec system");
 }
 
 
@@ -426,8 +428,27 @@ void FGElectricalSystem::bind ()
 void FGElectricalSystem::unbind ()
 {
     _serviceable_node.reset();
+    _volts_out.reset();
+    _amps_out.reset();
 }
 
+void FGElectricalSystem::deleteComponents(comp_list& comps)
+{
+    std::for_each(comps.begin(), comps.end(),
+                  [](FGElectricalComponent* comp) {
+                      delete comp;
+                  });
+
+    comps.clear();
+}
+
+void FGElectricalSystem::shutdown()
+{
+    deleteComponents(suppliers);
+    deleteComponents(buses);
+    deleteComponents(outputs);
+    deleteComponents(connectors);
+}
 
 void FGElectricalSystem::update (double dt)
 {

src/Systems/electrical.hxx

@@ -66,7 +66,7 @@ protected:
 
 public:
     FGElectricalComponent();
-    virtual ~FGElectricalComponent() {}
+    virtual ~FGElectricalComponent() = default;
 
     inline const std::string& get_name() { return name; }
 
@@ -222,6 +222,7 @@ public:
     // Subsystem API.
     void bind() override;
     void init() override;
+    void shutdown() override;
     void unbind() override;
     void update(double dt) override;
 
@@ -238,6 +239,8 @@ protected:
     typedef vector<FGElectricalComponent *> comp_list;
 
 private:
+    void deleteComponents(comp_list& comps);
+
     std::string name;
     int num;
     std::string path;