compressibleTwoPhaseEulerFoam tutorials: Updated fvSchemes and improved naming of kineticTheory stress correction

Supports separate turbulence models for each phase
Complete Lahey k-epsilon model provided
kineticTheory and particle-pressure models folded into same turbulence framework
by the addition of phase-pressure functions

compressibleTwoPhaseEulerFoam: Improved handling of compressibility effect on continuity and boundedness

Moved the snappyHexMesh tutorials to the appropriate solver directories and created links.