blockMesh: Change default location of blockMeshDict from constant/polyMesh to system

For multi-region cases the default location of blockMeshDict is now system/<region name>

If the blockMeshDict is not found in system then the constant directory
is also checked providing backward-compatibility

tutorials/incompressible/boundaryFoam/boundaryWallFunctions/system/blockMeshDict

@@ -0,0 +1,92 @@
+/*--------------------------------*- C++ -*----------------------------------*\
+| =========                 |                                                 |
+| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
+|  \\    /   O peration     | Version:  dev                                   |
+|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
+|    \\/     M anipulation  |                                                 |
+\*---------------------------------------------------------------------------*/
+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    object      blockMeshDict;
+}
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+convertToMeters 0.05;
+
+vertices
+(
+    (0 -1 0)
+    (0 0 0)
+    (0 1 0)
+    (0.1 -1 0)
+    (0.1 0 0)
+    (0.1 1 0)
+    (0 -1 0.1)
+    (0 0 0.1)
+    (0 1 0.1)
+    (0.1 -1 0.1)
+    (0.1 0 0.1)
+    (0.1 1 0.1)
+);
+
+blocks
+(
+    hex (0 3 4 1 6 9 10 7) (1 40 1) simpleGrading (1 1 1)
+    hex (1 4 5 2 7 10 11 8) (1 40 1) simpleGrading (1 1 1)
+);
+
+edges
+(
+);
+
+boundary
+(
+    lowerWall
+    {
+        type wall;
+        faces
+        (
+            (0 3 9 6)
+        );
+    }
+
+    upperWall
+    {
+        type wall;
+        faces
+        (
+            (2 8 11 5)
+        );
+    }
+
+    front
+    {
+        type cyclic;
+        neighbourPatch back;
+        faces
+        (
+            (9 3 4 10)
+            (10 4 5 11)
+        );
+    }
+
+    back
+    {
+        type cyclic;
+        neighbourPatch front;
+        faces
+        (
+            (0 6 7 1)
+            (1 7 8 2)
+        );
+    }
+);
+
+mergePatchPairs
+(
+);
+
+// ************************************************************************* //