ENH: basic i-j-k Field container (#1216)

- this is a simple container for fields with i-j-k addressing.

  It does not support field operations directly, but is primarily
  intended to be used when assembling field information with i-j-k
  logic. After assembly, the field can be transferred to a regular
  field for normal operations.  Eg,

      IjkField<scalar> assemble({15, 16, 200});

      // .. fill in i-j-k fields

      Field<scalar> final(std::move(assemble));
      assemble.clear();   // be pedantic
      ...

applications/test/IjkField/Make/files

@@ -0,0 +1,3 @@
+Test-IjkField.C
+
+EXE = $(FOAM_USER_APPBIN)/Test-IjkField

applications/test/IjkField/Make/options

@@ -0,0 +1,4 @@
+EXE_INC = -DFULLDEBUG
+
+/* EXE_INC = -I$(LIB_SRC)/finiteVolume/lnInclude */
+/* EXE_LIBS = -lfiniteVolume */

applications/test/IjkField/Test-IjkField.C

@@ -0,0 +1,138 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2019 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Description
+    Functionality of IjkField
+
+\*---------------------------------------------------------------------------*/
+
+#include "point.H"
+#include "IjkField.H"
+#include "IOstreams.H"
+
+using namespace Foam;
+
+template<class T>
+Ostream& print(const IjkField<T>& fld)
+{
+    Info<< static_cast<const Field<T>&>(fld).size()
+        << " " << fld.sizes() << ' ' << flatOutput(fld);
+
+    return Info;
+}
+
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+// Main program:
+
+int main(int argc, char *argv[])
+{
+    // Create with inconsistent sizes
+    IjkField<label> field0({1, 2, 3}, identity(10));
+
+    IjkField<scalar> field1({3, 4, 5});
+    IjkField<scalar> field2({2, 3, 3});
+
+    forAll(field1, i)
+    {
+        field1[i] = -i;
+    }
+    forAll(field2, i)
+    {
+        field2[i] = i;
+    }
+
+    Info<< "ijk field "; print(field1) << nl;
+    Info<< "ijk field "; print(field2) << nl;
+
+    field1.resize(field2.sizes());
+
+    Info<< "resized "; print(field1) << nl;
+
+    field1 *= 2;
+
+    Info<< "Multiply: "; print(field1) << nl;
+
+    field1.resize({1, 2, 3});
+
+    Info<< "Resize - shrink: "; print(field1) << nl;
+
+    field1.resize({2, 3, 2});
+
+    Info<< "Resize - grow: "; print(field1) << nl;
+
+    field1.resize({3, 2, 2});
+
+    Info<< "Resize - repartition: "; print(field1) << nl;
+
+    field1 = field2;
+
+    Info<< "Copied: "; print(field1) << nl;
+
+    field1 = 3.14159;
+
+    Info<< "Assigned: "; print(field1) << nl;
+
+    field1 += 3.14159;
+
+    Info<< "+= operator: "; print(field1) << nl;
+
+    field1 /= 1.2;
+
+    Info<< "/= operator: "; print(field1) << nl;
+
+    // Field operations are still limited, but we can bypass things too
+
+    {
+        Field<scalar>& tmpField = field1;
+        tmpField = sqr(tmpField);
+
+        Info<< "squared (workaround): "; print(field1) << nl;
+    }
+
+
+    Info<< nl
+        << "Before transfer: addr:" << long(field1.data())
+        << " size:" << field1.size() << nl;
+
+    Field<scalar> sfield1(std::move(field1));
+    field1.clear();
+
+    Info<< "After transfer to regular field" << nl
+        << "    source:" << long(field1.data()) << nl
+        << "    target:" << long(sfield1.data()) << nl
+        << "Values"
+        << "    source:";
+    print(field1) << nl;
+
+    Info<< "    target:" << flatOutput(sfield1) << nl;
+
+
+    Info << "\nEnd\n" << endl;
+
+    return 0;
+}
+
+
+// ************************************************************************* //