Improve management of fiducial list (for example in IsolatedWatershedImageFilter)

[jcfr]

See here http://www.na-mic.org/Bug/view.php?id=4065#c13578 for details.

• When going in fiducial mode. It is easy to add two fiducials to the same markup list. The filter ends running with the same coordinate for both seed because it took the first point of the same list selected twice.
• May be this could be improved by detecting when two time the same list selected. Instead of hiding the input box for coordinate. May be selecting the input box could simply be the coordinate of the selected fiducial. If you manually set some value ... it update the location of the fiducial on the screen.

[blowekamp]

Thanks for the feedback. As I recall you desired behavior was the original behavior with the old fiducialls, but it changed with the new Annotation nodes. This is the block of code that needs a change:
https://github.com/SimpleITK/SlicerSimpleFilters/blob/master/SimpleFilters/SimpleFilters.py#L662-L710