functionObjects::fluidMaxDeltaT: New functionObject to set the maximum Courant number and time-step

at Function1s of time.

Underlying this new functionObject is a generalisation of the handling of the
maximum time-step in the modular solvers to allow complex user-specification of
the maximum time-step used in a simulation, not just the time-dependency
provided by fluidMaxDeltaT but functions of anything in the simulation by
creating a specialised functionObject in which the maxDeltaT function is
defined.

The chemical and combustion time-scale functionObjects adjustTimeStepToChemistry
and adjustTimeStepToCombustion have been updated and simplified using the above
mechanism.

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

@@ -299,6 +299,19 @@ Foam::scalar Foam::functionObjectList::timeToNextAction()
 }
 
 
+Foam::scalar Foam::functionObjectList::maxDeltaT() const
+{
+    scalar result = vGreat;
+
+    forAll(*this, oi)
+    {
+        result = min(result, operator[](oi).maxDeltaT());
+    }
+
+    return result;
+}
+
+
 bool Foam::functionObjectList::read()
 {
     bool ok = true;