[Fedora-packaging] Updates to Eclipse Plugin packaging guidelines

Hi, I have a few updates to the Eclipse Plugin packaging guidelines. They include some clarifications, typos, and updates for Eclipse 3.4.x. The only bit of real substance is modifying the template to note how we're using the dropins mechanism for plugin installation in 3.4.x and above. I've attached a diff 'cause I don't think I can commit it. Can someone else? Thanks, Andrew