[FEM] add current density constraint

- also add corresponding App::PropertyCurrentDensity

- also fix a typo in test_object.py

src/App/Application.cpp

@@ -1914,6 +1914,7 @@ void Application::initTypes()
     App::PropertyAcceleration       ::init();
     App::PropertyForce              ::init();
     App::PropertyPressure           ::init();
+    App::PropertyCurrentDensity     ::init();
     App::PropertyElectricPotential  ::init();
     App::PropertyVacuumPermittivity ::init();
     App::PropertyInteger            ::init();

src/App/PropertyUnits.cpp

@@ -20,9 +20,7 @@
  *                                                                         *
  ***************************************************************************/
 
-
 #include "PreCompiled.h"
-
 #ifndef _PreComp_
 # include <cfloat>
 #endif
@@ -88,7 +86,6 @@ Base::Quantity PropertyQuantity::createQuantityFromPy(PyObject *value)
     return quant;
 }
 
-
 void PropertyQuantity::setPyObject(PyObject *value)
 {
     // Set the unit if Unit object supplied, else check the unit
@@ -140,7 +137,6 @@ const boost::any PropertyQuantity::getPathValue(const ObjectIdentifier & /*path*
 TYPESYSTEM_SOURCE(App::PropertyQuantityConstraint, App::PropertyQuantity)
 
 
-
 void PropertyQuantityConstraint::setConstraints(const Constraints* sConstrain)
 {
     _ConstStruct = sConstrain;
@@ -151,7 +147,6 @@ const char* PropertyQuantityConstraint::getEditorName() const
     return "Gui::PropertyEditor::PropertyUnitConstraintItem";
 }
 
-
 const PropertyQuantityConstraint::Constraints*  PropertyQuantityConstraint::getConstraints() const
 {
     return _ConstStruct;
@@ -253,6 +248,18 @@ PropertyDistance::PropertyDistance()
     setUnit(Base::Unit::Length);
 }
 
+//**************************************************************************
+//**************************************************************************
+// PropertyCurrentDensity
+//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+TYPESYSTEM_SOURCE(App::PropertyCurrentDensity, App::PropertyQuantity)
+
+PropertyCurrentDensity::PropertyCurrentDensity()
+{
+    setUnit(Base::Unit::CurrentDensity);
+}
+
 //**************************************************************************
 //**************************************************************************
 // PropertyElectricPotential

src/App/PropertyUnits.h

@@ -172,6 +172,19 @@ public:
     ~PropertyDistance() override = default;
 };
 
+/** CurrentDensity property
+ * This is a property for electric current densities. It is basically a float
+ * property. On the Gui it has a quantity of Ampere/m^2.
+ */
+class AppExport PropertyCurrentDensity: public PropertyQuantity
+{
+    TYPESYSTEM_HEADER_WITH_OVERRIDE();
+
+public:
+    PropertyCurrentDensity();
+    ~PropertyCurrentDensity() override = default;
+};
+
 /** ElectricPotential property
  * This is a property for electric potentials. It is basically a float
  * property. On the Gui it has a quantity of Volt.