Add option to administrator that show different help pages for each role of user

[sfai05]

Admin can set permission to a help post that only show the post to specific role of users

[adam-stokes]

Nice, @markjaquith any thought on getting these merged?

[leonho]

+1 @markjaquith this is a very useful feature in a production env when there are more than one type of user in the system (which is the purpose of having WP roles). For instance, editor can only see what editor needs to know. This allows to scale the help content without overwhelming users with irrelevant help content.