[App] add property for electric potentials

- in preparation to fix the electrostatic simulation mess

src/App/Application.cpp

@@ -1912,6 +1912,7 @@ void Application::initTypes()
     App ::PropertyAcceleration      ::init();
     App ::PropertyForce             ::init();
     App ::PropertyPressure          ::init();
+    App ::PropertyElectricPotential ::init();
     App ::PropertyVacuumPermittivity::init();
     App ::PropertyInteger           ::init();
     App ::PropertyIntegerConstraint ::init();

src/App/PropertyUnits.cpp

@@ -339,6 +339,18 @@ PropertyForce::PropertyForce()
     setUnit(Base::Unit::Force);
 }
 
+//**************************************************************************
+//**************************************************************************
+// PropertyElectricPotential
+//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+TYPESYSTEM_SOURCE(App::PropertyElectricPotential, App::PropertyQuantity)
+
+PropertyElectricPotential::PropertyElectricPotential()
+{
+    setUnit(Base::Unit::ElectricPotential);
+}
+
 //**************************************************************************
 //**************************************************************************
 // PropertyVacuumPermittivity

src/App/PropertyUnits.h

@@ -252,6 +252,18 @@ public:
     virtual ~PropertyForce(){}
 };
 
+/** ElectricPotential property
+ * This is a property for electric potentials. It is basically a float
+ * property. On the Gui it has a quantity of Volt.
+ */
+class AppExport PropertyElectricPotential : public PropertyQuantity
+{
+    TYPESYSTEM_HEADER();
+public:
+    PropertyElectricPotential(void);
+    virtual ~PropertyElectricPotential() {}
+};
+
 /** VacuumPermittivity property
  * This is a property for representing vacuum permittivity. It is basically a float
  * property. On the Gui it has a quantity like s^4*A^2 / (m^3*kg).