STYLE: fix indentation, doc

Fix an improperly indented bracket.
Update a doxygen see also note to refer to the
correct method.

Issue #3367
ENH: add the ruler projection widget

Add the ruler projection widget from the Annotations module.
Make the fiducial point projection widget more general
so that it can work with rulers to control the end point
projections.
Update the show/hide of widgets depending on markup type.

Issue #3367