and two-phase functionality separated from multiphase functionality

Multi-species, mass-transfer and reaction support and multi-phase
structure provided by William Bainbridge.

Integration of the latest p-U and face-p_U algorithms with William's
multi-phase structure is not quite complete due to design
incompatibilities which needs further development.  However the
integration of the functionality is complete.

The results of the tutorials are not exactly the same for the
twoPhaseEulerFoam and reactingTwoPhaseEulerFoam solvers but are very
similar.  Further analysis in needed to ensure these differences are
physical or to resolve them; in the meantime the twoPhaseEulerFoam
solver will be maintained.

twoPhaseEulerFoam/interfacialModels/heatTransferModels/sphericalHeatTransfer: new heat-transfer model

Model which applies an analytical solution for heat transfer from the
surface of a sphere to the fluid within the sphere.

Provided by William Bainbridge

BUG: mantis #1365: switched to using wall reflection to calculate wall normals, and added caching of the wall values

before:
    - 'new' prefixed to camel-cased class name: eg, someClass -> newSomeClass
    - 'New' prefixed to templated class name:   eg, TmplClass -> NewTmplClass
    - 'New' suffixed to class name:             eg, someClass -> someClassNew

after:
    - consistent 'New' suffixed to class name, no change of case
          eg, someClass -> someClassNew
          eg, TmplClass -> TmplClassNew