Restrict Player Interfaces

This release adds support for these interfaces:

• Player Interface (Random Things)
• Creative Player Interface (Random Things)
• Player Interface (Actually Additions)

This release makes the Introspection module safe to use with existing scripts. The previous behavior was to error upon getting an inventory object for a restricted player, and to return no transfer locations on inventory objects for restricted players. Now, for restricted players, no error occurs when getting an inventory object, and the existing inventory and ender_chest transfer locations point to empty, read-only inventories, instead of being removed.