This allows for mods to create there own Shear-like items
and have them interact with Blocks/Entities without extra work.
Also, if your block/entity supports the Shears, this allows you
to support mod-shears as well.
Performs the shear function on this object.
This is called for both client, and server.
The object should perform all actions related to being sheared,
except for dropping of the items, and removal of the block.
As those are handled by ItemShears itself.
Returns a list of items that resulted from the shearing process.
For entities, they should trust there internal location information
over the values passed into this function.
item - The ItemStack that is being used, may be empty.
world - The current world.
pos - If this is a block, the block's position in world.
fortune - The fortune level of the shears being used.
A List containing all items from this shearing. May be empty.