Maint/puppet 4/document event manager

This adds documentation to `Puppet::Transaction::EventManager` and `Puppet::Resource::Status` and removes some dead attributes from `Status`.
no that is the definition of the resource Notify[hello] - there is no declaration anywhere that says "there is going to be a Notify[hello] in the catalog at some point, I don't know how it will be defined yet" (nevermind that the full definition may not be at that source location since it can be mutated if virtual, etc. etc.), it is still a definition, not a declaration...