Silk-touch Spawners

[josefbaltz]

Implement an in-house solution for silk spawners

Describe the solution you'd like
Allow for players with silk touch pickaxes to get spawners.
Additionally create an API so external plugins can utilize our solution to this issue.

Stretch Goals
Implement a GUI to allow players to add items and other resources to change the spawner type after placed. For example, allow the player to spend 5 levels of experience and 16 gunpowder to set the spawner type to creeper.

Additional context
Utilize NBT tags to store mob type.
API should allow the following

• Creating an ItemStack with the required NBT data so the GalaxeSMP plugin can appropriately set the spawner type when placed.
• Adding required NBT data to an already existing spawner within someone's inventory.
• Easily get the mob type of an ItemStack