finite area integration

This merge includes the finite-area port from Hrvoje Jasak, a number of integration fixes and preliminary post-processing of finite area meshes/fields.

References

Tukovic, Z: The Finite Volume Method on Domains of Changeable Shape, PhD Thesis, University of Zagreb, Croatia, 2005

Tuković, Željko; Jasak, Hrvoje. A moving mesh finite volume interface tracking method for surface tension dominated interfacial fluid flow. Computers & fluids. 55 (2012) ; 70-84

src/finiteArea/finiteArea/fac/facDdt.C

@@ -53,7 +53,7 @@ ddt
     (
         mesh,
         mesh.schemesDict().ddtScheme("ddt(" + dt.name() + ')')
-    )().facDdt(dt);
+    ).ref().facDdt(dt);
 }
 
 
@@ -68,7 +68,7 @@ ddt
     (
         vf.mesh(),
         vf.mesh().schemesDict().ddtScheme("ddt(" + vf.name() + ')')
-    )().facDdt(vf);
+    ).ref().facDdt(vf);
 }
 
 
@@ -87,7 +87,7 @@ ddt
         (
             "ddt(" + rho.name() + ',' + vf.name() + ')'
         )
-    )().facDdt(rho, vf);
+    ).ref().facDdt(rho, vf);
 }
 
 
@@ -106,7 +106,7 @@ ddt
         (
             "ddt(" + rho.name() + ',' + vf.name() + ')'
         )
-    )().facDdt(rho, vf);
+    ).ref().facDdt(rho, vf);
 }