ItemGrid: fixed changing item count when ToRemove == CurrentCount

Fixes FS #380

git-svn-id: http://mc-server.googlecode.com/svn/trunk@1545 0a769ca7-a7f5-676a-18bf-c427514a06d6
Added cItem copy-constructor to Lua API, made cItem::IsEqual() and IsStackable() enchantment-aware

git-svn-id: http://mc-server.googlecode.com/svn/trunk@1546 0a769ca7-a7f5-676a-18bf-c427514a06d6