ENH: Lagrangian - added new PatchInteractionFields cloud function object

Creates volume fields whose boundaries are used to store patch interaction
statistics.

Current field output per patch face:
- \<cloud\>\<model\>:count - cumulative particle hits
- \<cloud\>\<model\>:mass - cumuluative mass of hitting particles

Fields can be reset according to:
- none: fields are not reset
- timeStep: reset at each time step
- writeTime: reset at each write time

Usage

    patchInteractionFields1
    {
        type            patchInteractionFields;
        resetMode       writeTime;
    }