Resolves bug-report http://bugs.openfoam.org/view.php?id=2356

Replaced the 'postProcess' argument to the 'write' and 'execute'
functions with the single static member 'postProcess' in the
functionObject base-class.

  - Avoids the need for the 'OutputFilterFunctionObject' wrapper
  - Time-control for execution and writing is now provided by the
    'timeControlFunctionObject' which instantiates the processing
    'functionObject' and controls its operation.
  - Alternative time-control functionObjects can now be written and
    selected at run-time without the need to compile wrapped version of
    EVERY existing functionObject which would have been required in the
    old structure.
  - The separation of 'execute' and 'write' functions is now formalized in the
    'functionObject' base-class and all derived classes implement the
    two functions.
  - Unnecessary implementations of functions with appropriate defaults
    in the 'functionObject' base-class have been removed reducing
    clutter and simplifying implementation of new functionObjects.
  - The 'coded' 'functionObject' has also been updated, simplified and tested.
  - Further simplification is now possible by creating some general
    intermediate classes derived from 'functionObject'.

Construction failure and recovery is not handled with exceptions in functionObjectList

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".

Also write out snapped location.

	probes, sampledSets and sampledSurfaces

Add support for constructing VectorSpaces from forms with lower component type,
e.g. Vector<scalar> from Vector<label>

Add support for constructing VectorSpaces from forms with lower component type,
e.g. Vector<scalar> from Vector<label>

This reverts commit c5bea524.

This reverts commit b18f6cc1.

- adjust code to more closely resemble sampledSets / sampledSurfaces

- added end() method to functionObject, functionObjectList & associated classes
- moved outputFilters from src/sampling -> src/OpenFOAM/db/functionObjects