Portraitsets define details for the automatic generation of special icon resources used to represent character portraits.
Each portraitset defines a name, a base graphic and a mask graphic used to mask out a suitable shape out of the rectangular image
file selected by the user.
The icon resources will be named portrait_[identity identifier]_[portraitset name] where the identity identifier
is the identifier string for the identity whose portrait file is being generated, as returned by e.g. User.getCurrentIdentity.
It is also possible to generate portrait tokens based on the portrait set.
The name of the icon resource that will be used as the background image
The name of the icon resource that will be used as a transparency mask for the portrait image
If specified, a token matching the icon will be created