ENH: give annotations option to be visible only in selected views

This uses the same convention used in dislay nodes for other
displayable managers (e.g. VolumeRendering), except that it uses the
sliceNode since it is the 2D analog to the 3D view Node (at some point
perhaps there should be a generic superclass).  Here, since we are only
using the ID string it doesn't matter what type the node it.

This feature allows custom UIs, for example where some annotations only
show up in one view while others show up everywher.  In particular, this
is helpful for annotations representing volume-specific anatomical
landmark locations.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21740 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: update dataprobe even when mousing over annotation

Increase the priority to get all events, even if they will later
be used by another observer.  Also be sure to observe the interactor
rather than the interactor style so the priority will work with
respect to widgets which observe the interactor itself.  The
interactor style is observing the interactor so this is the same
for the purposes of the data probe.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21741 3bd1e089-480b-0410-8dfb-8563597acbee