MythicInventories

- "type" option now takes in an MM item. - Minor cleanup

- Item serialization, storage, & additional options - Added initial implementation of item serialization and storage. - Added "interactable" option, allows for users to set which slots can be interacted with. - Added "save" option, allows for users to set which slots the plugin should save internally. - Added some extra methods to the MythicInventory class, new internal name method to hold the internal inventory name. - Lots of cleaning up, much more remains to be done. - Added new MM "openinventory" mechanic - Made MM soft-dependency - Removed all imports of MM in favor of direct method references, allows for easier checking of the presence of MM. - Moved MM mechanic registration to its own class. - Updated documentation in README file - Minor change: the inventory name will now be set to "Container" if it was not set in the config rather than the ID of the inventory.