ENH: Updated general construction of gravity field for applications. See #1094

Note that the field is now registered on time as opposed to the mesh

src/finiteVolume/cfdTools/general/include/fvCFD.H

@@ -21,6 +21,7 @@
 #include "findRefCell.H"
 #include "IOMRFZoneList.H"
 #include "constants.H"
+#include "gravityMeshObject.H"
 
 #include "columnFvMesh.H"
 

src/finiteVolume/cfdTools/general/include/readGravitationalAcceleration.H

@@ -1,12 +1,2 @@
-    Info<< "\nReading g" << endl;
-    uniformDimensionedVectorField g
-    (
-        IOobject
-        (
-            "g",
-            runTime.constant(),
-            mesh,
-            IOobject::MUST_READ_IF_MODIFIED,
-            IOobject::NO_WRITE
-        )
-    );
+Info<< "\nReading g" << endl;
+const meshObjects::gravity& g = meshObjects::gravity::New(runTime);