/** Initializes an instance of the ExtensionItem class.
* @param key The name of the extension item (e.g. ssl_cert).
* @param exttype The type of Extensible that this ExtensionItem applies to.
/** Initializes an instance of the ExtensionItem class.
* @param key The name of the extension item (e.g. ssl_cert).
* @param exttype The type of Extensible that this ExtensionItem applies to.