Contentish type interface.
$Id: Contentish.py,v 1.5 2003/01/06 20:37:41 yuppie Exp $
General interface for "contentish" items.
These methods need to be implemented by any class that wants to be a first-class citizen in the Portal Content world.
PortalContent implements this interface.
SearchableText is called to provide the Catalog with textual information about your object. It is a string usually generated by concatenating the string attributes of your content class. This string can then be used by the catalog to index your document and make it findable through the catalog.