Try and get rid of the bootstrapping

[rom1504]

For example, we need blocks.json and items.json in the blocks extractor in order to understand "drops" block and item names.
In order to avoid the dependency to blocks.json it would be needed to get all the block<->id relation before trying to get the drops.
To avoid the items.json dependency, just run the extraction function that get the item<->id relation before getting the drops.

Similar things are done in several other places.

Depending on old data is a bad idea.