Refs #7061. Initial work on responding to workspace changes.
Refs #7061. Making things update rather than reconstruct.
Refs #7061. Handling multiple peak sources.

This required adding a mechanism to the vtkPeaksSource plugin to get the
workspace name. Also, necessitated moving a function in ViewBase from private
to public.
Merge branch 'feature/7061_vsi_workspace_obs' into develop