- Added new base class for group feeds - GxsGroupFeedItem
- Added feed item for channel group
- Added test of feed items for channels and forums
- Reworked existing feed items

git-svn-id: http://svn.code.sf.net/p/retroshare/code/trunk@7689 b45a01b8-16f6-495d-af2f-9b41ad6348cc