Clang format run on near-the-header lines.

Happy New Year

[HT] Modified the velocity calculation in order that it can be used for both the monolithic and staggered schemes.

[HT] Moved the computation of the coefficients of the heat transport equation to two new member functions.

[HT] Changed the name and the type of the material property member of HT, and

took the forward declaration of the type of that member.

[Coupling] Modified the process definitions in Process/HT for the assembly for both of the monolithic scheme and the staggered scheme.

FluidProperties is a process independent container
for common fluid properties like density, viscosity
and specific heat capacity.

This potentially saves a second copy compared to using const
reference. See Effective Modern C++, Item 41.