The registry holds repositories, models and scenarios. set_default_registry()
records which object, in which environment, energyRt should use;
which_registry() reports it, and get_registry() returns the object itself,
creating it if it does not exist yet.
Usage
set_default_registry(obj_name = "registry", env_name = ".scen")
use_registry(obj_name = "registry", env_name = ".scen")
which_registry()
get_registry()Value
which_registry() a list with name and env; get_registry() the
registry object; set_default_registry() the previous value, invisibly.
The current registry object.
