Fields now correspond to the initial residual for the first solver
iteration

Residual fields can be written using the new 'writeFields' entry, e.g.

    functions
    {
        residual
        {
            type            residuals;
            libs            ("libutilityFunctionObjects.so");
            fields          (".*");
            writeControl    writeTime;
            writeFields     true;
        }
    }

Fields currently correspond to the initial residual for the last solver
iteration.

-dry-run : perform check only and no writing
-dry-run-write: perform check and write to the next time step.  This
also triggers function objects that fire on the call to write()

- this is consistent with compiler defaults, and helps Darwin users

- resolve in favour of "inline explicit", which had marginally more
  uses and provides consistent prefixing for inline methods.

- make the purpose more explicit, and reduces some work for the
  compiler as well.

- improves backward compatibility and more naming consistency.
  Retain setMany(iter1, iter2) to avoid ambiguity with the
  PackedList::set(index, value) method.

- required for std::iterator_traits specialization, which is used by
  the std::max_element algorithm on Darwin.

- move constructable
- factory methods: New, NewFrom
- reset methods