* Replace the rome classes by equivalent com.rometools classes, breaking
 the API of the feed plugin.
* Add a much simpler implementation of XWikiFeedFetcher as feed fetching
 has been removed in ROME 2 and the caching logic wasn't used. Make
 XWikiFeedFetcher internal as it doesn't need to be public, and it
 changed completely, anyway.
* Work around a change in the API of SyndEntry#setContributors.
* Remove all traces of ROME 1.