Fixed StackOverflowError when shift clicking item in custom inventory - BUKKIT-1929, BUKKIT-2532

Fixes [#BUKKIT-2532] and [#BUKKIT-1929], caused by not removing clicked item and falling into infinite loop. Fixed by overriding Container.b(int i).
https://bukkit.atlassian.net/browse/BUKKIT-1929
https://bukkit.atlassian.net/browse/BUKKIT-2532 **(Test Plugin Here)**