Add support for while style blocks.

Some messages have a repeating block of data until a condition isn't met, like:
https://github.com/themeldingwars/AeroMessages/blob/8fbd6008707aa2b321d18e32ebebca172c8a7b5b/Scripts/GSS/Character/GSS_Character_BaseController_InventoryUpdate.cs#L41

Need to figure out a way to handle these.