ENH: Added ViewGroup property to view nodes

ViewGroup is used for restricting scope of:

• linked slice view property changes (is slices are linked, a property change will only change views in the same group)
• crosshair jump to slice (if crosshair is moved with shift+mousemove and slice jump is enabled, only those slices will be moved that are in the same group as the view where the mouse was)
• slice intersection display (slice intersections will only shown of those slices that are in the same group)

Implementation:

• Added new ViewGroup member to abstract view node (string, empty by default)
• In default layouts "Three over three" and "Four over four" separated top/bottom rows (view IDs changed to Red+, Yellow+, Green+, 1+; unique node IDs were necessary because on layout change view group is not updated, so we cannot share view nodes between layouts the same group ID for all views)
• Updated vtkMRMLSliceNode::JumpAllSlices to only jump those slices that have matching viewgroup
• Updated vtkMRMLSliceLinkLogic::OnMRMLNodeModified(vtkMRMLNode* node) to make aware of groups
• Updated slice displayable manager to only show slice intersections in the same group (and mapped in layout)
• Updated 2D/3D displayable managers to only jump those slices on crosshair update (shift+mousemove) that are in the same group
• Updated GUI:
  Added View group view/edit to View Controllers module (Advanced section).
  Added viewGroup property to simple markups widget (that can restrict slice jumping to a specific view group)
• Added crosshair jump slice speed test to PerformanceTests module

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25591 3bd1e089-480b-0410-8dfb-8563597acbee