Updates to MooseVariableInterface and variable getter APIs to incorporate vector finite elements

Needs to wait for https://github.com/idaholab/moose/pull/10238

include/userobjects/NekSideIntegralVariableUserObject.h

@@ -31,7 +31,7 @@ InputParameters validParams<NekSideIntegralVariableUserObject>();
  */
 class NekSideIntegralVariableUserObject :
   public SideIntegralUserObject,
-  public MooseVariableInterface
+  public MooseVariableInterface<Real>
 {
 public:
   NekSideIntegralVariableUserObject(const InputParameters & parameters);
@@ -39,7 +39,7 @@ public:
 protected:
   virtual Real computeQpIntegral() override;
   virtual void finalize() override;
-    
+
   /// Holds the solution at current quadrature points
   const VariableValue & _u;
   /// Legendre polynomial object. TODO address dynamic casting of this object

src/userobjects/NekSideIntegralVariableUserObject.C

@@ -38,7 +38,7 @@ NekSideIntegralVariableUserObject::NekSideIntegralVariableUserObject(const Input
     // TODO we really shouldn't have to dynamic cast into FourierPolynomial and Legendre Polynomial here
     // but this was a quick example
     SideIntegralUserObject(parameters),
-    MooseVariableInterface(this, false),
+    MooseVariableInterface<Real>(this, false),
     _u(coupledValue("variable")),
     _legendre_poly_function(dynamic_cast<LegendrePolynomial&>(_mci_feproblem.getFunction(parameters.get<std::string>("legendre_function_name")))),
     _fourier_poly_function(dynamic_cast<FourierPolynomial&>(_mci_feproblem.getFunction(parameters.get<std::string>("fourier_function_name")))),
@@ -49,7 +49,7 @@ NekSideIntegralVariableUserObject::NekSideIntegralVariableUserObject(const Input
     _coupled_grad(coupledGradient("variable")),
     _diffusion_coefficient(getMaterialProperty<Real>("diffusion_coefficient_name")),
     _surface_area_pp(getPostprocessorValueByName(parameters.get<std::string>("surface_area_pp")))
-                            
+
 {
   addMooseVariableDependency(mooseVariable());
 
@@ -64,8 +64,8 @@ NekSideIntegralVariableUserObject::NekSideIntegralVariableUserObject(const Input
   {
     mooseError("Need to implement logic for l direction not equal to 2");
   }
-  
-  
+
+
 }
 
 Real