BUG: move to Annotations conversion rather than over-registering Markups nodes

Registering markups nodes with the annotation node tags was breaking the
ruler nodes, as they inherit heavily from the point nodes.
Instead move to a semi-automatic conversion (using a ctk message box that
allows the user to specify always convert) of annotation fiducials to markup
fiducial lists. Search the scene for annotation fiducials, collect the hierarchies
in which they appear and move the annotation fiducials into markup fiducial list
nodes (removing 1:1 hierarchy nodes, display and storage nodes).
Add a note to the Annotations module that fiducials have been moved to Markups.
Provide a manual conversion button in the Advanced panel to convert fiducials,
and updated documentation.
Make the Data module edit properties link for Annotation fiducials go to the
Markups module.
Removed Annotation fiducials from the mouse place tool bar. Set the Markups
fiducial name to be just Fiducial.
Disabled the scene reading test, replaced it with a conversion test.