polyCellSet: General cell set selection class

Description
    General cell set selection class for models that apply to sub-sets
    of the mesh.

    Currently supports cell selection from a set of points, a specified cellSet
    or cellZone or all of the cells.  The selection method can either be
    specified explicitly using the \c selectionMode entry or inferred from the
    presence of either a \c cellSet, \c cellZone or \c points entry.  The \c
    selectionMode entry is required to select \c all cells.

Usage
    Examples:
    \verbatim
        // Apply everywhere
        selectionMode   all;

        // Apply within a given cellSet
        selectionMode   cellSet; // Optional
        cellSet         rotor;

        // Apply within a given cellZone
        selectionMode   cellZone; // Optional
        cellSet         rotor;

        // Apply in cells containing a list of points
        selectionMode   points; // Optional
        points
        (
            (2.25 0.5 0)
            (2.75 0.5 0)
        );
    \endverbatim

Also used as the base-class for fvCellSet which additionally provides and
maintains the volume of the cell set.

tutorials/modules/incompressibleFluid/rotor2DRotating/constant/dynamicMeshDict

@@ -22,6 +22,8 @@ mover
 
     motionSolver    solidBody;
 
+    selectionMode   all;
+
     solidBodyMotionFunction  rotatingMotion;
 
     origin          (0 0 0);