Three blog entry plugins removed per discussion on dev ML.

git-svn-id: https://svn.apache.org/repos/asf/roller/trunk@1612180 13f79535-47bb-0310-9956-ffa450edef68
Removed no longer used base class of Wikipedia and Google Link plugins, it can be restored if we need it again in the future.

git-svn-id: https://svn.apache.org/repos/asf/roller/trunk@1612183 13f79535-47bb-0310-9956-ffa450edef68