Files in this directory are NBT data for use by the Builders Helper mod.

You can use the NBT in a file by specifying filename.nbt instead of {nbtdata} in your blueprints.

You can edit thse files using a utility such as 'nbtExplorer' 
http://www.minecraftforum.net/forums/mapping-and-modding/minecraft-tools/1262665-nbtexplorer-nbt-editor-for-windows-and-mac

To make it easier to understand, file names starting with:
 item_       item definitions (for CHEST contents)
 entity_     entities (for MOB directive, and SPAWNER potentials)
 potential_  spawn potentials (for SPAWNER potentials)
 spawner_    spawners (for SPAWNER directive)
 chest_      chest definitions (for CHEST directive)

You should also be able to use an entity or spawner file as a spawner potential; and a chest file as a chest item, as the NBT will be modified on the fly if necessary.

If an item has a string ID (minecraft 1.8) but is generated in minecraft 1.7, then the blueprint library will automatically convert it to a numerical ID where possible.

In general, unrecognised or invalid items will be converted to sticks.  Invalid spawners or spawn potentials will usually cause the spawner to be rendered as air (since it can result in a crash under minecraft 1.7); however where possible it will be changed to spawn Chickens.  Minecraft 1.8 will change an invalid spawner to a pig spawner.


