Fix "/itemc modify infinite" permission

Fix the "/itemc modify infinite" permission to be "itemcase.create.infinite" in the plugin.yml.
Fix NullPointer on Itemcase create (Fixes ItemCase-44)

Fix the null pointer thrown when a player tries to create an itemcase with the command "/itemc create" with nothing in their hand.
Update language files

Update language files to fix typos etc.
Drop Itemcase storage when infinite changed to true

Drop Itemcases storage when infinite changed to true from false.