Added some basic options to the GUI opened when a player left clicks a display case. Only the owner of the item which is currently held in a display case is able to change the options.

Cycling options

• Its super easy to cycle through the options, and through the settings which each option has. In the GUI, left clicking the blue slot will change the option that you're currently editing, and right clicking will cycle through the settings currently supported for said option.
• As mentioned, only the owner of the item can use these.

Options added

• Billboard - changing this option will cycle between center and fixed
• Show name - changing this will cycle between showing or hiding the name and owner text display