Make unlimited max_stack_size as default value

[Nordsoft91]

Make max_stack_size unlimited if not defined in protoset for StackedInventory

[kyle-wannacott]

I think max_stack_size should be one by default, I guess it depends on the genre of game...

[peter-kish]

Yeah, it depends on the particular use case, though I still think that 100 (the default in v2.4.10) is not really useful.

This is changed in v3.0.0, where all items are considered item stacks where the default maximum stack size is one.

[peter-kish]

Version 3.0.0 has been released and the default stack_size and max_stack_size is 1.