Investigate phase transition workflow

[greenstack]

Do phases really need delta time for Begin and End methods?

Should default phase managers automatically call these Begin and End methods? That would be my expected behavior.

[greenstack]

Thinking about this, I think Begin and End methods shouldn't have a delta time, but there could maybe be UpdatePhaseBeginning and UpdatePhaseEnding methods that allow the developer to do animations. That said, there's the whole "every change should be tied to an action" paradigm that I'm considering enforcing.