Hard code the SimObject::Params struct

Hard code the SimObject::Params struct

sim/sim_object.cc:
    Add a new constructor that can take the params struct and
    tweak the old one to create a params struct if we use the
    old constructor.
sim/sim_object.hh:
    Hard code a Params struct for SimObject that all other params
    structs can derive from.  Move the name string into the struct
    and update the code accordingly.  New constructor that takes
    the params struct.

--HG--
extra : convert_revision : 30761dab31d7257f9e8c864dcd6cae37309163f2