MDL-26405 restore - dispatch able to skip branches
after this change any restore_structure_step processor method is able to instruct the dispatcher about to skip any path below it. Until now, we were doing the checks on each child processor method, but that was inneficient and prone to errors (easy to miss the check in a child so some orphaned piezes of restore may be causing mess here and there). Once implemented, it's simlpy a matter of the parent deciding if all its children must be processed or no. Easier for developers and also small speed improvement because avoids unnecesary dispatching/processing to happen. Surely only will be used in parts of core, like in question_categories, saving 50-60 sub processors (sub-paths) to be dispatched.