functionObjectList: Improved flexibility of field argument parsing

Additional flexibility for handling of field arguments has been extended
to dictionary lists of field settings, as well as word lists of field
names. This means that the following syntax is now supported:

    postProcess -func "fieldAverage(p, U { prime2Mean on; }, T)"

    postProcess -func "fieldAverage(fields=(p U { prime2Mean on; } T))"

src/OpenFOAM/db/functionObjects/functionObjectList/wordAndDictionary.C

@@ -0,0 +1,79 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Copyright (C) 2020 OpenFOAM Foundation
+     \\/     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/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "wordAndDictionary.H"
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+Foam::wordAndDictionary::wordAndDictionary(Istream& is)
+:
+    Tuple2<word, dictionary>()
+{
+    is >> *this;
+
+    is.check("wordAndDictionary::wordAndDictionary(Istream& is)");
+}
+
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::wordAndDictionary::~wordAndDictionary()
+{}
+
+
+// * * * * * * * * * * * * * * Friend Operators * * * * * * * * * * * * * * //
+
+Foam::Istream& Foam::operator>>(Istream& is, wordAndDictionary& wd)
+{
+    wd.first() = word(is);
+    wd.second().clear();
+
+    token t(is);
+    is.putBack(t);
+
+    if (t.isPunctuation() && t.pToken() == token::BEGIN_BLOCK)
+    {
+        dictionary d(is);
+        wd.second().transfer(d);
+    }
+
+    return is;
+}
+
+
+Foam::Ostream& Foam::operator<<(Ostream& os, const wordAndDictionary& wd)
+{
+    os << wd.first();
+
+    if (!wd.second().empty())
+    {
+        os << token::SPACE << wd.second();
+    }
+
+    return os;
+}
+
+
+// ************************************************************************* //