use SPI-level bean interface in Preferences SPI rather than the parser-level API

git-svn-id: https://svn.apache.org/repos/asf/wookie/trunk@1565647 13f79535-47bb-0310-9956-ffa450edef68
added SPI for widget metadata

git-svn-id: https://svn.apache.org/repos/asf/wookie/trunk@1565649 13f79535-47bb-0310-9956-ffa450edef68