Variables definition

Here is definition of variables which can be referred by this document entirely.

Variable	Type	Description
$CASSIOPEIA_HOME	String	Cassiopeia's home directory.
$LANG_KEY	String	Language key (Terminological code of ISO 639-2).
$MODULE_ID	String	Identifier for each module. It is used for Ruby's class name, don't use illegal naming.
$SHOP_NAME	String	Shop's user name.