COM: Separate htc FO from general FO and reactingEuler solvers (#1714)

The phase systems tables for multiphase solvers create conflict
between each other as they are defined in the same namespace and using
similar class names.

Therefore a special htc function object for reactingEulerSolver was
added (reactingEulerHtcModel), located under
src/phaseSystemModels/reactingEulerFoam/functionObjects/

This commit includes the following:

- Relocate solvers/reactingEulerFoam functionObjects to
  src/phaseSystemModels
- Remove links for fieldFunctionObject to multiphase libs to avoid
  conflicts
- New FO for htc for reactingEulerFoam called reactingEulerHtcModel