ENH: Extend Halo datatype with mass/type/owner

Added more bits of info to the halo data-structure to
distinguish halos by type, i.e., NORMAL, GHOST, ZOMBIE.
Further, an owner ID is added, i.e., a unique block
identifier within the DIY runtime environment used to
reconcile tracking results from the neighbors to the
owners. Last, mass is now saved in the data-structure.
ENH: Add RHO_C critical density in global defs
ENH: Parameter parsing & redshift calculation

Added functionality to parse an indat.params file.
Rank 0 reads and broadcasts its contents to all
other ranks. Further, implement mapping of timestep
to red-shift.