For blocks, we now use 'block-item state' and 'block-only state', which should be much clearer for people implementing custom stuff.
'block-item state', as the name suggests, sticks to the item when the block is acquired as an item.
'block-only state' applies only to the block and is discarded when the block is acquired as an item.
'type data' for items was also renamed, since 'type' is too ambiguous to be anything but super confusing.
This reverts commit f64dc01bd1.
I forgot that the ItemBlock constructor implicitly strips off any states
of the origin block, which is something that we unfortunately can't do
any other way right now, since the blocks don't remember their default
states.
