I have added a new block the HtmlContextualBlock. The goal is to display the a content that varies according to the fileId that the user is using.
The main Attributes are :
MenuName : by default it is "_menu", this is the name of the entry searched relatively to the current fileId
DefaultContent : the text displayed when no menu is found, by default it is "No menu"
If the user points on a fileId like /a/b/c/index, it will first look at /a/b/c/_menu, otherwise it will use /_menu (for instance if the user is using the forum bb module). In all case if no content is found, it will display the content in the attribute DefaultContent which is "No menu"