Fix object initialization issues by making sure all objects defined in YAML steering are initialized at start

In the current system of evolutions, evolutions are created only when they are first requested, and do not exist before that. Evolutions that do not exist yet do not receive at-iteration updates. The problem was that APPLgrid was accessing its input evolutions first in compute(). Since compute() is called after atIteration() updates, these evolutions would not get at-iteration update before they are used at first iteration, leading to a crash.