[Finishes #80927658] Allow variable create/edit/delete to be disabled on a per-level basis

The fix for #80927658 was a little more complex than just making getUserBlocks() return blocks that are not editable.  Modifying getUserBlocks would've affected the block count.  I added a config option so editing of variables can be disabled, while keeping the block marked as editable.
I'm wrong about needing to save it to prevent it from being changed.  In both cases it happens in init.  Removing the extra var.