ENH: add some standard templates and macros into stdFoam.H

- some functionality similar to what the standary library <iterator>
  provides.

  * stdFoam::begin() and stdFoam::end() do type deduction,
    which means that many cases it is possible to manage these types
    of changes.

    For example, when managing a number of indices:
       Map<labelHashSet> lookup;

    1) Longhand:

        for
        (
            Map<labelHashSet>::const_iterator iter = lookup.begin();
            iter != lookup.end();
            ++iter
        )
        { .... }

    1b) The same, but wrapped via a macro:

        forAllConstIter(Map<labelHashSet>, lookup, iter)
        { .... }

    2) Using stdFoam begin/end templates directly

        for
        (
            auto iter = stdFoam::begin(lookup);
            iter != stdFoam::end(lookup);
            ++iter
        )
        { .... }

    2b) The same, but wrapped via a macro:

        forAllConstIters(lookup, iter)
        { .... }

Note that in many cases it is possible to simply use a range-based for.
Eg,
     labelList myList;

     for (auto val : myList)
     { ... }

     for (const auto& val : myList)
     { ... }

These however will not work with any of the OpenFOAM hash-tables,
since the standard C++ concept of an iterator would return a key,value
pair when deferencing the *iter.

The deduction methods also exhibits some slightly odd behaviour with
some PtrLists (needs some more investigation).

applications/test/HashTable/Test-hashTable.C

@@ -62,7 +62,7 @@ int main()
     Info<< "\ntable1 sortedToc: " << table1.sortedToc() << endl;
     table1.printInfo(Info)
         << "table1 [" << table1.size() << "] " << endl;
-    forAllConstIter(HashTable<scalar>, table1, iter)
+    forAllConstIters(table1, iter)
     {
         Info<< iter.key() << " => " << iter() << nl;
     }
@@ -106,7 +106,7 @@ int main()
         << "\ntable3" << table3 << nl;
 
     Info<< "\nerase table2 by iterator" << nl;
-    forAllIter(HashTable<scalar>, table2, iter)
+    forAllIters(table2, iter)
     {
         Info<< "erasing " << iter.key() << " => " << iter.object() << " ... ";
         table2.erase(iter);