Sort out correct order of blocks in perfect foresight Ramsey and document it

Usually steady after initval computes a steady state. But with ramsey_model, one seems to need the ramsey_model(planner_discount=0.99); statement before the call to steady and therefore initval. Also, it is not clear what steady does in this case. Is it the private sector equilibrium steady state or the Ramsey steady state that is computed. Relevant test case: optimal_policy/nk_ramsey_det.mod