Interface restructured to use the ICON-C init/run/finalize low-level interface

This is a relatively simple change to make muphys comply with ICON-C's low-level init/run/finalize interface convention. As agreed in the ICON-C modularization team, physical constants are passed to graupel_init, rather than shared from a central model, and these are put into the Graupel 'state'. Some complexity arises from the use of constants (PARAMETERs), which are derived from the physical parameters. These derived quantities have become simple local variables, and are derived in the code section rather than in a PARAMETER declaration.

There was also a cosmetic bug: als and alv were imported twice from mo_physical_constants. This is now fixed.