ENH: Added new particleZoneInfo cloud function object.

Reports cloud information for particles passing through a specified cell
zone.

Example usage:

    cloudFunctions
    {
        particleZoneInfo1
        {
            type            particleZoneInfo;
            cellZone        leftFluid;

            // Optional entries
            //writer          vtk;
        }
    }

Results are written to file:
- \<case\>/postProcessing/lagrangian/\<cloudName\>/\<functionName\>/\<time\>

    \# cellZone        : leftFluid
    \# time            : 1.0000000000e+00
    \#
    \# origID    origProc    (x y z)    time0    age    d0    d    mass0    mass

Where
- origID : particle ID
- origProc : processor ID
- (x y z) : Cartesian co-ordinates
- time0 : time particle enters the cellZone
- age : time spent in the cellZone
- d0 : diameter on entry to the cellZone
- d : current diameter
- mass0 : mass on entry to the cellZone
- mass : current mass

If the optional \c writer entry is supplied, cloud data is written in the
specified format.

During the run, output statistics are reported after the cloud solution,
e.g.:

    particleZoneInfo:
        Cell zone                       = leftFluid
        Contributions                   = 257

Here, 'Contributions' refers to the number of incremental particle-move
contributions recorded during this time step. At write times, the output
is extended, e.g.:

    particleZoneInfo:
        Cell zone                       = leftFluid
        Contributions                   = 822
        Number of particles             = 199
        Written data to "postProcessing/lagrangian/reactingCloud1/

TUT: filter: add an example for the particleZoneInfo function object