Book of Familiars

• Added the ability for released entities to return to the book after death. Note: the entity MUST have been stored and released at some point for this to work.
• Released entities will go on cooldown for a default of 20 minutes (changeable in config).
• You can use xp to skip the cooldown, default is 5 levels (changeable in config).
• If your book is full or the entity dies while you're offline, it is added to a pending list and will appear in your book either when there is space or on next login.
• Added a delete button. This will permanently remove the familiar from the world, but there is a confirm screen to avoid accidents. 
• Added a check on player login for the removal of stored familiars that no longer exist (e.g. if their respective mod was uninstalled). Can be disabled in config.

As always, the update is backwards compatible but I would still recommend a world backup before updating.