Updated option list
Put advection classes into new format
Put forward declarations in model header to reduce the compilation
times and put cross section class into the correct format
Put the new structure in the buffer structure
Update the force and timeloop class
Put pressure solvers in new format
Put the grid in the new format
Use forward declaration in the advection class
Put forward declarations in diffusion class
Put forward declarations in boundary class
Use forward declarations in pressure solver
Forward declaration in grid
Forward declarations in force
Cleaned up model.h
Removed the 42-scheme...
Completed comments in advection header
Commented the boundary header
Put the new option values in advection
Updated the input file with the correct advection options
Update the diffusion with new names