Adding config only check flag and helper function

In some event generation jobs, knowing if the job will be configuration only is important. If we're in configuration only mode, we skip certain operations that consume significant CPU. The option already exists both in "old-style" running and in CA mode; this simply adds a helper function (that optionally takes the configuration flags, so that it will be an easy migration for users) that checks if we're running in that mode.

At the same time, adding a few extra comments to code, and renaming the logger in MCJobOptionUtils for a little more clarity (it's not MG, after all).