functionObjects: Moved into the functionObjects namespace and rationalized and simplified failable construction

Rather than requiring each functionObject to handle failed construction
internally (using the active_ flag) the static member function "viable"
is provided which returns true if construction of the functionObject is
likely to be successful.  Failed construction is then handled by the
wrapper-class which constructs the functionObject,
e.g. "OutputFilterFunctionObject".

etc/codeTemplates/dynamicCode/functionObjectTemplate.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011-2013 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -76,6 +76,18 @@ ${typeName}FunctionObject::${typeName}FunctionObject
 }
 
 
+bool ${typeName}FunctionObject::viable
+(
+    const word& name,
+    const objectRegistry& obr,
+    const dictionary& dict,
+    const bool
+)
+{
+    return true;
+}
+
+
 // * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
 
 ${typeName}FunctionObject::~${typeName}FunctionObject()

etc/codeTemplates/dynamicCode/functionObjectTemplate.H

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011-2013 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -102,6 +102,16 @@ public:
             const bool loadFromFilesUnused = false
         );
 
+        //- Construct for given objectRegistry and dictionary.
+        //  Allow the possibility to load fields from files
+        static bool viable
+        (
+            const word& name,
+            const objectRegistry& unused,
+            const dictionary&,
+            const bool loadFromFilesUnused = false
+        );
+
 
     //- Destructor
     virtual ~${typeName}FunctionObject();

etc/codeTemplates/functionObject/FUNCTIONOBJECT.C

@@ -71,21 +71,15 @@ void Foam::FUNCTIONOBJECT::read(const dictionary& dict)
 
 
 void Foam::FUNCTIONOBJECT::execute()
-{
-    // Do nothing - only valid on write
-}
+{}
 
 
 void Foam::FUNCTIONOBJECT::end()
-{
-    // Do nothing - only valid on write
-}
+{}
 
 
 void Foam::FUNCTIONOBJECT::timeSet()
-{
-    // Do nothing - only valid on write
-}
+{}
 
 
 void Foam::FUNCTIONOBJECT::write()