The diameter of the drops formed are obtained from the local capillary
length multiplied by the \c dCoeff coefficient which defaults to 3.3.

Reference:
    Lefebvre, A. (1988).
    Atomization and sprays
    (Vol. 1040, No. 2756). CRC press.

surfaceFilmModels::BrunDrippingInjection: New dripping model based on the Rayleigh-Taylor stability analysis
of film flow on an inclined plane by Brun et.al.

    Brun, P. T., Damiano, A., Rieu, P., Balestra, G., & Gallaire, F. (2015).
    Rayleigh-Taylor instability under an inclined plane.
    Physics of Fluids (1994-present), 27(8), 084107.

- separated out the geometry handling into the 'regionModels' library
- regionModels currently includes single layer and 1-D regions
- surface film modelling over-hauled

This reverts commit c5bea524.

This reverts commit b18f6cc1.

- film approximated as single layer mesh, generated using
  extrudeToRegionMesh utility

- library implemented in a hierarchy similar to lagrangian/intermediate:
  - currently includes kinematic and thermodynamic variants

- sub-models include:
  - film detachment/dripping
  - phase change (place holder only)

- works in parallel

- currently in beta status

- exception calcType.H since it'll most likely be used for building
  applications anyhow

- use quailified names in more of the lagrangian code

- killed some tab indents in various places.