ENH: add Function1 wrapping for functionObject trigger

Returns a 0/1 value corresponding to function object trigger levels.

    Usage:
    \verbatim
        <entryName> functionObjectTrigger;
        <entryName>Coeffs
        {
            triggers        (1 3 5);
            defaultValue    false;  // Default when no triggers activated
        }
    \endverbatim

ENH: add reset() method for Constant Function1

ENH: allow forced change of trigger index

- the triggers are normally increase only,
  but can now override this optionally

src/OpenFOAM/db/functionObjects/stateFunctionObject/stateFunctionObject.C

@@ -74,12 +74,9 @@ Foam::dictionary& Foam::functionObjects::stateFunctionObject::propertyDict()
 }
 
 
-bool Foam::functionObjects::stateFunctionObject::setTrigger
-(
-    const label triggeri
-)
+void Foam::functionObjects::stateFunctionObject::clearTrigger()
 {
-    return stateDict().setTrigger(triggeri);
+    return stateDict().clearTrigger();
 }
 
 
@@ -89,6 +86,16 @@ Foam::label Foam::functionObjects::stateFunctionObject::getTrigger() const
 }
 
 
+bool Foam::functionObjects::stateFunctionObject::setTrigger
+(
+    const label triggeri,
+    bool increaseOnly
+)
+{
+    return stateDict().setTrigger(triggeri, increaseOnly);
+}
+
+
 bool Foam::functionObjects::stateFunctionObject::foundProperty
 (
     const word& entryName