[Development] Update the AlgoCG parameter of the configuration

[sblauth]

At the moment, the parameters for the nonlinear CG methods are specified, e.g., as

cg_periodic_restart = True
cg_periodic_its = 5
cg_relative_restart = False
cg_restart_tol = 0.5

So boolean parameters are used to activate certain behaviors and double parameters are used for specifying tolerances / iterations. This should be refactored, so that only the keys cg_periodic_restart = 5 is used (and a value of 0 means that this is not active), analogously for cg_restart_tol.