ENH: improved consistency of surface writers (#1232)

- remove writeGeometry() in favour of write() and make it pure virtual
  so that all writers must explicitly deal with it.

- establish proxy extension at construction time and treated as an
  invariant thereafter. This avoids potentially surprising changes in
  behaviour when writing.

applications/test/surfaceWriter/Make/files

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

applications/test/surfaceWriter/Make/options

@@ -0,0 +1,5 @@
+EXE_INC = \
+    -I$(LIB_SRC)/surfMesh/lnInclude
+
+EXE_LIBS = \
+    -lsurfMesh

applications/test/surfaceWriter/Test-surfaceWriter.C

@@ -0,0 +1,115 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  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/>.
+
+Application
+    Test-surfaceWriter
+
+Group
+    grpSurfaceUtilities
+
+Description
+    Test surface writers.
+
+Usage
+    \b Test-surfaceWriter inputFile outputFile
+
+\*---------------------------------------------------------------------------*/
+
+#include "argList.H"
+#include "surfaceWriter.H"
+#include "MeshedSurfaces.H"
+
+using namespace Foam;
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+int main(int argc, char *argv[])
+{
+    argList::addNote
+    (
+        "convert between surface formats, "
+        "but primarily for testing functionality\n"
+        "Normally use surfaceMeshConvert instead."
+    );
+
+    argList::noParallel();
+    argList::noFunctionObjects();
+
+    argList::addOption
+    (
+        "type",
+        "writerType"
+    );
+
+    argList::addArgument("inputFile");
+    argList::addArgument("outputFile");
+
+    #include "setRootCase.H"
+
+    const fileName importName = args[1];
+    const fileName exportName = args[2];
+
+    if (importName == exportName)
+    {
+        FatalErrorInFunction
+            << "Output file " << exportName << " would overwrite input file."
+            << exit(FatalError);
+    }
+
+
+    if (!MeshedSurface<face>::canRead(importName, true))
+    {
+        return 1;
+    }
+
+    const word writerType =
+        args.lookupOrDefault<word>("type", exportName.ext());
+
+    auto surfWriter = surfaceWriter::New(writerType);
+
+    {
+        MeshedSurface<face> surf(importName);
+
+        Info<< "Read surface:" << endl;
+        surf.writeStats(Info);
+
+        Info<< "Open " << exportName
+            << " for writing with " << surfWriter->type() << nl;
+
+        surfWriter->open
+        (
+            surf.points(),
+            surf.surfFaces(),
+            exportName.lessExt(),
+            false // serial
+        );
+
+        surfWriter->write();
+    }
+
+    Info<< "\nEnd\n" << endl;
+
+    return 0;
+}
+
+// ************************************************************************* //