update getComunityBookmarks

deleted bookmark files in Communityservice , the getCommunityBookmarks wrapper now uses BookmarkService getAllBookmarks and BookmarkList to fetch the bookmarks, updated the sample also to reflect this change.

-deleted Bookmark.java under communities folder
-deleted BookmarkList.java under communities folder
-deleted BookmarkFeedHandler.java under communities folder
-updated getAllBookmarks 
-updated communityBookmarks sample